describe discharge tube experiment with labelled diagram

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Discovery Of Electron | Discharge Tube Experiment

Discharge tube.

The discharge tube is a glass tube having two electrodes sealed into it connected to a vacuum pump to reduce the pressure of the gas taken into it. A slit is placed in the tube to get a sharp beam of radiations.

Experiment:

William Crooks a British scientist studied the passage of electricity through gases taken at different pressures in the gas discharge tube. He observed that air taken in the gas discharge tube at ordinary pressure did not allow the electricity to flow, even when a source of high potential of about 5000 Volt was used. However, when pressure of air was reduced by removing most of the air from the discharge tube then it allowed the current to flow and emitted light (as in neon sign). When pressure was reduced further to about 0.01 torr, then emission of light by air ceased. But the current still flows between the electrodes and produced fluorescent on striking the glass walls opposite to the cathode. This was the result of rays emitted by cathode . Rays emitted by cathode when electricity is passed through a gas taken in the discharge tube at very low pressure are called cathode rays.

Discovery of electron

Emission of cathode rays does not depend on the nature of the electrodes or the gas used in the discharge tube. This indicates that cathode rays (i.e., electrons) are the constituents of all types of matter.

Conclusion:

J.J. Thomson calculated the mass of cathode rays. He suggested that these rays are matter and not electromagnetic radiations. He proposed the name corpuscles for these particles. But as these particles were similar to the particles present in on the electricity, therefore, later on they were named electrons. J.J. Thomson won the 1906 Nobel Prize.

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Cathode Rays ( AQA A Level Physics )

Revision note.

Cathode Rays

What is a cathode.

• An electrode is a conductor through which electricity passes
• A cathode is a  negatively charged electrode
• An anode is a  positively charged electrode

Discharge Tubes

• These were glass chambers containing a low pressure gas, with an anode at one end and a cathode at the other, connected to a high voltage supply
• It was hypothesised that this glow was caused by emissions from the cathode, called  cathode rays

A discharge tube

What are Cathode Rays?

• This showed they were made from  negatively charged particles

How does the Discharge Tube Conduct?

• The electric field between the electrodes ionises the gas particles in the tube
• Negative electrons are attracted to the positive anode
• Positive ions are attracted to the negative cathode
• This can only happen because the pressure of the gas is low enough to allow the charged particles to travel
• Conduction is a result of these electrons and positive ions moving across the tube

Why does the Gas Glow?

• Due to the  low pressure , they have space to gain a large amount of energy in their kinetic store
• When they collide, they recombine in an  excited  state
• The electrons in atoms de-excite to ground state, emitting visible photons (as well as other frequencies)

Worked example

A discharge tube contains a low pressure gas. An anode is at one end and a cathode at the other with a large potential difference between the two. The gas conducts and also emits light.

(i) Explain how the gas conducts, referring to the charge-carrying particles in your answer. 

(ii) Explain why the gas must be at low pressure to emit light. 

Step 1: Recall that, for the gas to conduct, we need charged particles

• The electric field ionises gas atoms, removing electrons and forming positive ions
• The cathode also emits electrons (at very high potential difference)

Step 2: Recall why the particles move across the discharge tube

• The electric field accelerates electrons and positive ions, which cause conduction

Step 1: Light is emitted when electrons and ions recombine

• Positive ions and electrons collide at high speed and recombine, emitting photons when they de-excite

Step 2: Light is emitted when an atom is excited

• Accelerated electrons collide with gas atoms, exciting them
• The gas atoms emit visible photons when they de-excite

Step 3: Describe a low pressure gas in terms of the distribution of particles

• In a low pressure gas, the particles are widely spaced

Step 4: Recall why this allows atoms to become excited more easily

• There are fewer obstacles for accelerating charged particles, so they can collide with enough energy to produce excited atoms (which then go on to emit light)

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The Mechanism of Light Production by a Gas Discharge Tube

30.2 Discovery of the Parts of the Atom: Electrons and Nuclei

Learning objectives.

By the end of this section, you will be able to:

• Describe how electrons were discovered.
• Explain the Millikan oil drop experiment.
• Describe Rutherford’s gold foil experiment.
• Describe Rutherford’s planetary model of the atom.

Just as atoms are a substructure of matter, electrons and nuclei are substructures of the atom. The experiments that were used to discover electrons and nuclei reveal some of the basic properties of atoms and can be readily understood using ideas such as electrostatic and magnetic force, already covered in previous chapters.

Charges and Electromagnetic Forces

In previous discussions, we have noted that positive charge is associated with nuclei and negative charge with electrons. We have also covered many aspects of the electric and magnetic forces that affect charges. We will now explore the discovery of the electron and nucleus as substructures of the atom and examine their contributions to the properties of atoms.

The Electron

Gas discharge tubes, such as that shown in Figure 30.4 , consist of an evacuated glass tube containing two metal electrodes and a rarefied gas. When a high voltage is applied to the electrodes, the gas glows. These tubes were the precursors to today’s neon lights. They were first studied seriously by Heinrich Geissler, a German inventor and glassblower, starting in the 1860s. The English scientist William Crookes, among others, continued to study what for some time were called Crookes tubes, wherein electrons are freed from atoms and molecules in the rarefied gas inside the tube and are accelerated from the cathode (negative) to the anode (positive) by the high potential. These “ cathode rays ” collide with the gas atoms and molecules and excite them, resulting in the emission of electromagnetic (EM) radiation that makes the electrons’ path visible as a ray that spreads and fades as it moves away from the cathode.

Gas discharge tubes today are most commonly called cathode-ray tubes , because the rays originate at the cathode. Crookes showed that the electrons carry momentum (they can make a small paddle wheel rotate). He also found that their normally straight path is bent by a magnet in the direction expected for a negative charge moving away from the cathode. These were the first direct indications of electrons and their charge.

The English physicist J. J. Thomson (1856–1940) improved and expanded the scope of experiments with gas discharge tubes. (See Figure 30.5 and Figure 30.6 .) He verified the negative charge of the cathode rays with both magnetic and electric fields. Additionally, he collected the rays in a metal cup and found an excess of negative charge. Thomson was also able to measure the ratio of the charge of the electron to its mass, q e q e / m e / m e —an important step to finding the actual values of both q e q e and m e m e . Figure 30.7 shows a cathode-ray tube, which produces a narrow beam of electrons that passes through charging plates connected to a high-voltage power supply. An electric field E E is produced between the charging plates, and the cathode-ray tube is placed between the poles of a magnet so that the electric field E E is perpendicular to the magnetic field B B of the magnet. These fields, being perpendicular to each other, produce opposing forces on the electrons. As discussed for mass spectrometers in More Applications of Magnetism , if the net force due to the fields vanishes, then the velocity of the charged particle is v = E / B v = E / B . In this manner, Thomson determined the velocity of the electrons and then moved the beam up and down by adjusting the electric field.

To see how the amount of deflection is used to calculate q e / m e q e / m e , note that the deflection is proportional to the electric force on the electron:

But the vertical deflection is also related to the electron’s mass, since the electron’s acceleration is

The value of F F is not known, since q e q e was not yet known. Substituting the expression for electric force into the expression for acceleration yields

Gathering terms, we have

The deflection is analyzed to get a a , and E E is determined from the applied voltage and distance between the plates; thus, q e m e q e m e can be determined. With the velocity known, another measurement of q e m e q e m e can be obtained by bending the beam of electrons with the magnetic field. Since F mag = q e vB = m e a F mag = q e vB = m e a , we have q e / m e = a / vB q e / m e = a / vB . Consistent results are obtained using magnetic deflection.

What is so important about q e / m e q e / m e , the ratio of the electron’s charge to its mass? The value obtained is

This is a huge number, as Thomson realized, and it implies that the electron has a very small mass. It was known from electroplating that about 10 8 C/kg 10 8 C/kg is needed to plate a material, a factor of about 1000 less than the charge per kilogram of electrons. Thomson went on to do the same experiment for positively charged hydrogen ions (now known to be bare protons) and found a charge per kilogram about 1000 times smaller than that for the electron, implying that the proton is about 1000 times more massive than the electron. Today, we know more precisely that

where q p q p is the charge of the proton and m p m p is its mass. This ratio (to four significant figures) is 1836 times less charge per kilogram than for the electron. Since the charges of electrons and protons are equal in magnitude, this implies m p = 1836 m e m p = 1836 m e .

Thomson performed a variety of experiments using differing gases in discharge tubes and employing other methods, such as the photoelectric effect, for freeing electrons from atoms. He always found the same properties for the electron, proving it to be an independent particle. For his work, the important pieces of which he began to publish in 1897, Thomson was awarded the 1906 Nobel Prize in Physics. In retrospect, it is difficult to appreciate how astonishing it was to find that the atom has a substructure. Thomson himself said, “It was only when I was convinced that the experiment left no escape from it that I published my belief in the existence of bodies smaller than atoms.”

Thomson attempted to measure the charge of individual electrons, but his method could determine its charge only to the order of magnitude expected.

Since Faraday’s experiments with electroplating in the 1830s, it had been known that about 100,000 C per mole was needed to plate singly ionized ions. Dividing this by the number of ions per mole (that is, by Avogadro’s number), which was approximately known, the charge per ion was calculated to be about 1 . 6 × 10 − 19 C 1 . 6 × 10 − 19 C , close to the actual value.

An American physicist, Robert Millikan (1868–1953) (see Figure 30.8 ), decided to improve upon Thomson’s experiment for measuring q e q e and was eventually forced to try another approach, which is now a classic experiment performed by students. The Millikan oil drop experiment is shown in Figure 30.9 .

In the Millikan oil drop experiment, fine drops of oil are sprayed from an atomizer. Some of these are charged by the process and can then be suspended between metal plates by a voltage between the plates. In this situation, the weight of the drop is balanced by the electric force:

The electric field is produced by the applied voltage, hence, E = V / d E = V / d , and V V is adjusted to just balance the drop’s weight. The drops can be seen as points of reflected light using a microscope, but they are too small to directly measure their size and mass. The mass of the drop is determined by observing how fast it falls when the voltage is turned off. Since air resistance is very significant for these submicroscopic drops, the more massive drops fall faster than the less massive, and sophisticated sedimentation calculations can reveal their mass. Oil is used rather than water, because it does not readily evaporate, and so mass is nearly constant. Once the mass of the drop is known, the charge of the electron is given by rearranging the previous equation:

where d d is the separation of the plates and V V is the voltage that holds the drop motionless. (The same drop can be observed for several hours to see that it really is motionless.) By 1913 Millikan had measured the charge of the electron q e q e to an accuracy of 1%, and he improved this by a factor of 10 within a few years to a value of − 1 . 60 × 10 − 19 C − 1 . 60 × 10 − 19 C . He also observed that all charges were multiples of the basic electron charge and that sudden changes could occur in which electrons were added or removed from the drops. For this very fundamental direct measurement of q e q e and for his studies of the photoelectric effect, Millikan was awarded the 1923 Nobel Prize in Physics.

With the charge of the electron known and the charge-to-mass ratio known, the electron’s mass can be calculated. It is

Substituting known values yields

where the round-off errors have been corrected. The mass of the electron has been verified in many subsequent experiments and is now known to an accuracy of better than one part in one million. It is an incredibly small mass and remains the smallest known mass of any particle that has mass. (Some particles, such as photons, are massless and cannot be brought to rest, but travel at the speed of light.) A similar calculation gives the masses of other particles, including the proton. To three digits, the mass of the proton is now known to be

which is nearly identical to the mass of a hydrogen atom. What Thomson and Millikan had done was to prove the existence of one substructure of atoms, the electron, and further to show that it had only a tiny fraction of the mass of an atom. The nucleus of an atom contains most of its mass, and the nature of the nucleus was completely unanticipated.

Another important characteristic of quantum mechanics was also beginning to emerge. All electrons are identical to one another. The charge and mass of electrons are not average values; rather, they are unique values that all electrons have. This is true of other fundamental entities at the submicroscopic level. All protons are identical to one another, and so on.

The Nucleus

Here, we examine the first direct evidence of the size and mass of the nucleus. In later chapters, we will examine many other aspects of nuclear physics, but the basic information on nuclear size and mass is so important to understanding the atom that we consider it here.

Nuclear radioactivity was discovered in 1896, and it was soon the subject of intense study by a number of the best scientists in the world. Among them was New Zealander Lord Ernest Rutherford, who made numerous fundamental discoveries and earned the title of “father of nuclear physics.” Born in Nelson, Rutherford did his postgraduate studies at the Cavendish Laboratories in England before taking up a position at McGill University in Canada where he did the work that earned him a Nobel Prize in Chemistry in 1908. In the area of atomic and nuclear physics, there is much overlap between chemistry and physics, with physics providing the fundamental enabling theories. He returned to England in later years and had six future Nobel Prize winners as students. Rutherford used nuclear radiation to directly examine the size and mass of the atomic nucleus. The experiment he devised is shown in Figure 30.10 . A radioactive source that emits alpha radiation was placed in a lead container with a hole in one side to produce a beam of alpha particles, which are a type of ionizing radiation ejected by the nuclei of a radioactive source. A thin gold foil was placed in the beam, and the scattering of the alpha particles was observed by the glow they caused when they struck a phosphor screen.

Alpha particles were known to be the doubly charged positive nuclei of helium atoms that had kinetic energies on the order of 5 MeV 5 MeV when emitted in nuclear decay, which is the disintegration of the nucleus of an unstable nuclide by the spontaneous emission of charged particles. These particles interact with matter mostly via the Coulomb force, and the manner in which they scatter from nuclei can reveal nuclear size and mass. This is analogous to observing how a bowling ball is scattered by an object you cannot see directly. Because the alpha particle’s energy is so large compared with the typical energies associated with atoms ( MeV MeV versus eV eV ), you would expect the alpha particles to simply crash through a thin foil much like a supersonic bowling ball would crash through a few dozen rows of bowling pins. Thomson had envisioned the atom to be a small sphere in which equal amounts of positive and negative charge were distributed evenly. The incident massive alpha particles would suffer only small deflections in such a model. Instead, Rutherford and his collaborators found that alpha particles occasionally were scattered to large angles, some even back in the direction from which they came! Detailed analysis using conservation of momentum and energy—particularly of the small number that came straight back—implied that gold nuclei are very small compared with the size of a gold atom, contain almost all of the atom’s mass, and are tightly bound. Since the gold nucleus is several times more massive than the alpha particle, a head-on collision would scatter the alpha particle straight back toward the source. In addition, the smaller the nucleus, the fewer alpha particles that would hit one head on.

Although the results of the experiment were published by his colleagues in 1909, it took Rutherford two years to convince himself of their meaning. Like Thomson before him, Rutherford was reluctant to accept such radical results. Nature on a small scale is so unlike our classical world that even those at the forefront of discovery are sometimes surprised. Rutherford later wrote: “It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. On consideration, I realized that this scattering backwards ... [meant] ... the greatest part of the mass of the atom was concentrated in a tiny nucleus.” In 1911, Rutherford published his analysis together with a proposed model of the atom. The size of the nucleus was determined to be about 10 − 15 m 10 − 15 m , or 100,000 times smaller than the atom. This implies a huge density, on the order of 10 15 g/cm 3 10 15 g/cm 3 , vastly unlike any macroscopic matter. Also implied is the existence of previously unknown nuclear forces to counteract the huge repulsive Coulomb forces among the positive charges in the nucleus. Huge forces would also be consistent with the large energies emitted in nuclear radiation.

The small size of the nucleus also implies that the atom is mostly empty inside. In fact, in Rutherford’s experiment, most alphas went straight through the gold foil with very little scattering, since electrons have such small masses and since the atom was mostly empty with nothing for the alpha to hit. There were already hints of this at the time Rutherford performed his experiments, since energetic electrons had been observed to penetrate thin foils more easily than expected. Figure 30.11 shows a schematic of the atoms in a thin foil with circles representing the size of the atoms (about 10 − 10 m 10 − 10 m ) and dots representing the nuclei. (The dots are not to scale—if they were, you would need a microscope to see them.) Most alpha particles miss the small nuclei and are only slightly scattered by electrons. Occasionally, (about once in 8000 times in Rutherford’s experiment), an alpha hits a nucleus head-on and is scattered straight backward.

Based on the size and mass of the nucleus revealed by his experiment, as well as the mass of electrons, Rutherford proposed the planetary model of the atom . The planetary model of the atom pictures low-mass electrons orbiting a large-mass nucleus. The sizes of the electron orbits are large compared with the size of the nucleus, with mostly vacuum inside the atom. This picture is analogous to how low-mass planets in our solar system orbit the large-mass Sun at distances large compared with the size of the sun. In the atom, the attractive Coulomb force is analogous to gravitation in the planetary system. (See Figure 30.12 .) Note that a model or mental picture is needed to explain experimental results, since the atom is too small to be directly observed with visible light.

Rutherford’s planetary model of the atom was crucial to understanding the characteristics of atoms, and their interactions and energies, as we shall see in the next few sections. Also, it was an indication of how different nature is from the familiar classical world on the small, quantum mechanical scale. The discovery of a substructure to all matter in the form of atoms and molecules was now being taken a step further to reveal a substructure of atoms that was simpler than the 92 elements then known. We have continued to search for deeper substructures, such as those inside the nucleus, with some success. In later chapters, we will follow this quest in the discussion of quarks and other elementary particles, and we will look at the direction the search seems now to be heading.

PhET Explorations

Rutherford scattering.

How did Rutherford figure out the structure of the atom without being able to see it? Simulate the famous experiment in which he disproved the Plum Pudding model of the atom by observing alpha particles bouncing off atoms and determining that they must have a small core.

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• Cathode Ray Experiment

What are Cathode Rays?

Cathode rays are a beam of negatively charged electrons traveling from the negative end of an electrode to the positive end within a vacuum, across a potential difference between the electrodes.

How Do the Cathode Rays Work?

The cathode is a negative electrode, Anode is the positive electrode. Since electrons are repelled by the negative electrode, the cathode is the source of cathode rays inside a vacuum environment. When a potential difference is applied, the electrons jump to an excited state and travel at high speeds to jump back-and-forth inside the vacuum glass chamber and when some cathode rays certain molecules of the cathode screen, they emit light energy. A wire is connected from anode to cathode to complete the electrical circuit.

Construction of a Cathode Ray Tube

Its Basic Components are: -

Electron Gun Assembly: - It is the source of the electron beams. The electron gun has a heater, cathode, pre-accelerating anode, focusing anode and accelerating anode.

Deflecting Plates: - They produce a uniform electrostatic field only in one direction, and accelerate particles in only one direction.

Screen: - The inner layer of the screen is coated with phosphorus, and produces fluorescence when cathode rays hit the screen by a process of phosphorus excitation.

Aquadag: - It is an aqueous solution of graphite used to collect the secondary emitted electrons which are required to keep the cathode ray in electrical equilibrium.

What is the Cathode Ray Tube Experiment?

In 1897, great physician J.J. Thompson, conducted his first cathode ray tube experiment to prove that rays emitted from an electron gun are inseparable from the latent charge. He built his cathode ray tube with a metal cylinder on the other end. The metal had two small diversions(slits), leading to an electrometer that could measure a small electric charge. From the first experiment, he discovered that the electrometers stopped measuring electric charge. From this, he deduced that the electric charge and the cathode rays must be combined and are the same entity.

Then he conducted a Second experiment, to prove the charge carried by the cathode rays was negative or positive. Now, he put a negatively charged metal plate on one side of the cathode rays to go past the anode, and a positively charged metal plate on the other side. Instead of an electrometer at one end of the Cathode Ray Tube, he used a fluorescent coated tube that would glow where the cathode ray hit it. When the charged metal plates were introduced he found that the cathode rays bent away from the negative plate and towards the positive plate. This proved that the cathode rays were negatively charged.

Then he performed the third experiment, to know the nature of the particles and reduce the mass of the particles as they had too small of a mass to be calculated directly. For the experiment, he used the cathode ray tube and with a high applied potential difference between the two electrodes, with the negatively charged cathode producing the cathode rays. He had already deduced that the particles were negatively charged. Firstly, he applied an electric field in the path between anode and cathode and measured the deflections from the straight path. Now he applied a magnetic field across the cathode ray tube by using an external magnetic field. The cathode ray is deflected by the magnetic field. Now he changed the direction of the external magnetic field and found that the beam of electrons is deflected in the opposite direction. From this experiment, he concluded that the electrostatic deflection is the same as the electromagnetic deflection for the cathode rays and he was able to calculate the charge to mass ratio of the electron.

After these three experiments, he deduced that inside the atom there consist of a subatomic particle, originally named ‘corpuscle’, then changed to ‘electron’ which is 1800 times lighter than the mass of hydrogen atom (Lightest atom).

Formula Used

The derivation of the formula used to calculate the charge to the mass ratio:

For Electric Field the force on a particle is

Force(F)=Charge(Q)*Electric field(E) ---<1>

For Magnetic Field the force on a particle moving with velocity is:

F=q*velocity(v)*Magnetic Field(B) ---<2>

From 1 and 2 we get,

V=E/B ----<3>

From the definition of Force,

Acceleration(a)= Force(f)/mass(m) ----<4>

Combining 1 and 4

a=q*E/m ----<5>

From Newton’s law Of motion, vertical displacement is:

Y= (1/2)*a*t*t ----<6>

From 5 and 6

q/m=(2*y*v*v)/x*x*E

Cathode Ray Tubes (CRT) 

The cathode ray tube (CRT) is a vacuum tube, in which electrons are discharged from the cathode and accelerated through a voltage, and thereby gains acceleration of some 600 km/s for every volt. These accelerated electrons collide into the gas inside the tube, thereby allowing it to glow. This enables us to see the path of the beam. Helmholtz coil, a device for producing a region of nearly uniform magnetic field, is also used to apply a quantifiable magnetic field by passing a current through them.

A magnetic field will cause a force to act on the electrons which are perpendicular to both the magnetic field and their direction of travel. Thus, a circular path will be followed by a charged particle in a magnetic field. The faster the speed of a charged particle in a magnetic field, the larger the circle traced out in a magnetic field. Contrarily, the larger the magnetic field needed for a given radius of curvature of the beam. The paths of the electrons are distorted by the magnet in CRT Tv when they are brought near the screen. The picture on the screen appears when the electrons accurately hit phosphors on the back of the screen. Because of this, different colors of light are emitted on the screen when the electrons are impacted. Hence, the electrons are forced to settle in the wrong place, thereby causing the distortion of the image and the psychedelic colors.

Postulates of J.J. Thomson’s Atomic Model

After the Cathode ray tube experiment, Thomson gave one of the first atomic models including the newly discovered particle. 

His model stated: -

An atom resembles a sphere of positive charge with a negative charge present inside the sphere.

The positive charge and the negative charge were equal in magnitude and thus the atom had no charge as a whole and is electrically neutral.

His model resembles a plum pudding or watermelon. It assumed that positive and negative charge inside an atom is randomly spread across the whole sphere like the red part of the watermelon (positive charge) and the black seeds (negative charge).

Practical Uses of Cathode Ray Tube Experiment

In ancient times, the cathode ray tubes were used in the beam where the electron was considered with no inertia but have higher frequencies and can be made visible for a short time.

Many scientists were trying to get the secrets of cathode rays, while others were in search of the practical uses or applications of cathode ray tube experiments. And the first search was ended and released in 1897 which was introduced as Karl Ferdinand Braun’s oscilloscope. It was used for producing luminescence on a chemical affected screen in which cathode rays were allowed to pass through the narrow aperture by focusing into the beams that looked like a dot. This dot was passed for scanning across the screen which was represented visually by the electrical pulse generator. 

Then during the first two to three decades of the twentieth century, inventors continued to search the uses of cathode ray tube technology. Then inspired by Braun's oscilloscope, A. A. Campbell advised that a cathode ray tube would be used for projecting video images on the screen. But, this technology of the time did not get matched with the vision of Campbell-Swinton. It was only until 1922, when Philo T. Farnsworth developed a magnet to get focused on the stream of electrons on the screen, for producing the image. Thus, the first kind of it, Farnsworth, was quickly backed up by Zworykin’s kinescope, known as the ancestor of modern TV sets.

Nowadays, most image viewer devices are made with the help of cathode ray tube technology including the guns of electrons which are used in huge areas of science as well as medical applications. One such use for cathode-ray tube research is the microscope invented by Ernst Ruska in 1928. The microscope based on electrons uses the stream of electrons to magnify the image as the electrons have a small wavelength which is used for magnifying the objects which are very small to get resolved by visible light. Just like Plucker and Crookes work, Ernst Ruska used a strong field of magnetic lines for getting it focused on the stream of electrons into an image.

Solved Example:  

Question: The charge of an electron e=1.602∗10−19 and its is mass m=9.11∗10−31. The stopping potential of an electron traveling in a cathode ray tube is V=5V. Find the velocity of an electron traveling (where charge of an electron e=1.602∗10−19 and mass m=9.11810−31).

Answer: Here we need to find the velocity of traveling electrons using the given stopping potential.

We know that eV=12mv2, the charge(e) and mass(m) of the electron is also given as,

e=1.602∗10−19 and m=9.11∗10−31

By substituting the values of e, m, V.(1.602∗10−19)(5)

=12(9.11∗10−31)(v2)v2

=(1.602∗10−19)(5)(2)9.11∗10−31v

=1.33∗106m/s             

FAQs on Cathode Ray Experiment

1. What is the procedure of the Cathode Ray Experiment?

The apparatus of Cathode Ray Experiment is arranged in such a way that the terminals have high voltage with the internal pressure, which is reduced by removing the air inside the CRT. Because of the high voltage in the terminal,  the partial air inside it is ionized and hence gas becomes the conductor. The electric current propagates as a closed-loop circuit. In order to recognize and measure the ray produced, a dipole is set up. The cathode rays will begin deflecting and repel from the dipole and move towards the anode because of the dipole. The phosphorescent substance is arranged in such a way that the rays strike the substance. And hence, it causes small sparks of light, which detects the stream of rays.

2. What are Cathode ray tubes?

Cathode ray tubes (CRT) are a presentation screen that produces pictures as a video signal. Cathode ray tubes (CRT) is a type of vacuum tube that displays pictures when electron beams from an electron gun hit a luminous surface. The CRT produces electron beams, accelerates them at high speed, and thereby deflecting them to take pictures on a phosphor screen. Electronic presentation gadgets being the most established and least expensive electronic presentation innovation, were initially made with CRTs. CRTs work at any aspect ratio, at any resolution, and geometry without the need to resize the picture. CRTs work on the principle of an optical and electromagnetic phenomenon, called cathodoluminescence.

3. What are the applications of Cathode ray tubes?

The following are the applications of Cathode ray tubes.

The main components of a cathode ray tube (CRT) includes A Vacuum tube holding an electron cannon and a screen lined with phosphors.

The technology of Cathode ray tubes is used by Televisions and computer monitors. Three electron cannons correlate to corresponding types of phosphors in color CRTs, one for each main color viz red, green, and blue.

Ancient computer terminals and black and white televisions are examples of monochromatic CRTs.

cathode ray tube (CRT) is also used in oscilloscopes, which are machines that display and analyze the waveform of electronic signals.

A cathode ray amusement device was the very first video game to be produced, which were used in old military radar screens.

4. What are the basic principles of the CRT?

There are three basic principles of the CRT as the following:

Electrons are released into a vacuum tube from very hot metal plates.

The released electrons are accelerated and their direction of movement is controlled by using either a magnetic field from a coil that is carrying an electric current or by a voltage between metal plates.

A high-velocity beam of electrons hits some materials such as zinc sulfide. The spot is created on the fluorescent screen, and it causes material, called a phosphor, to glow, giving a spot of light as wide as the beam.

5.  How to understand the concept of the Cathode Ray Experiment easily?

Students can understand the concept of the Cathode Ray Experiment easily with the help of a detailed explanation of the Cathode Ray Experiment provided on Vedantu. Vedantu has provided here a thorough explanation of the Cathode Ray Experiment along with Cathode Rays, How Do the Cathode Rays Work, Construction of a Cathode Ray Tube, Postulates of J.J. Thomson’s Atomic Model, and Practical Uses of Cathode Ray Tube Experiment along with examples. Students can learn the concepts of all the important topics of Science subject on Vedantu.

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Cathode Ray Experiment

Arpita Srivastava

Content Writer

The cathode ray tube is a type of vacuum tube where an electron gun will emit electron beams, which will display images on a phosphorescent screen. It helps in converting an electrical signal into a visual display.

• Cathode ray experiments can easily produce electrons which move from one atom to another in the form of electric current .
• The electrons are accelerated from one end of the tube to another with the help of an electric field.
• When the electrons hit the farthest end of the tube, they discharge all the energy they carry due to their speed.
• A small quantity of energy is transformed into X-rays .
• It is most commonly used in our television set in the form of a picture tube.

Key Terms: Cathode Ray Experiment, Cathode Ray Tube, Electrical Signal, Electron, X-rays, Atoms, Heat, Energy, Electric current, Electric Field, Magnetic Field

What is Cathode Ray Tube?

[Click Here for Sample Questions]

Cathode Ray Tube is a vacuum tube where an electron beam, deflected by applied magnetic or electric fields, creates a trace on a fluorescent screen. It was invented in 1897 by the German physicist Karl Ferdinand Braun.

• It is a vacuum glass envelope containing an electron gun, a source of electrons and a fluorescent light.
• The tube will accelerate and redirect the electrons with the help of internal or external means.
• Light is created when electrons hit a fluorescent tube.
• The front area of the cathode ray tube is scanned repeatedly to generate a fixed pattern called a  raster.
• These tubes are used in memory devices and computer monitors. 
• Speed of cathode rays is comparatively slower than light.

J. J. Thomson Experiment – The Discovery of Electron

The cathode ray experiment was first conducted in 1878 by an English physicist, William Crookes. Later in the 19th century, J. J. Thomson studied the characteristics and the constituents of cathode rays.

• The cathode rays were deflected by electrical and magnetic fields. 
• This behaviour was similar to that of a negatively charged particle, which suggested that the rays contained electrons.
• A discharge tube, also called a 'Crookes tube,' is made up of glass with two metallic plates. 
• One end is connected to the positive terminal, and the other to the negative terminal of the high-voltage power supply. 
• The plate connected to the negative terminal is the cathode, and the plate connected to the positive terminal is the anode.
• An electrical current was passed in the discharge tube experiment at a high voltage with low pressure. 
• Due to this current, a stream of rays spreading from the cathode passed through the tube. 
• These rays were named as the cathode rays.

Apparatus Setup 

JJ Thomson started the work on the cathode ray experiment in the late 1800s. A cathode ray discharge tube is a cylindrical glass tube that consists of two metallic electrodes, namely an anode and a cathode.

• The electrodes are connected to a battery that will accelerate the electrons.
• The gas released in the tube is kept at a pressure of 0.0001 atm.
• The pressure inside the tube is maintained by a vacuum pump. 
• Cathode rays will move from cathode to anode in a straight line in the absence of an electric and magnetic field.
• It will get deflected when placed in a magnetic and electric field.

Cathode Ray Discharge Tube 

Procedure of the Experiment

The procedure of the experiment is as follows:

• The equipment is set up by passing a high source voltage of 10,000 volts.
• This, in return, will set up a low pressure inside the cathode ray discharge tubes.
• The tubes are converted into conductors of electricity by passing voltage through metallic electrodes.
• For the identification of rays, an additional dipole was set up inside the apparatus.
• This will result in the deflection of rays from the negative terminal to the positive terminal.
• The process was continued by placing the phosphorescent substance and producing the fluorescent display on the screen.

After completing the experiment, J.J. Thomson concluded that rays are negatively charged particles present or moving around in a set of positive charges. 

• This theory helped physicists further to understand the atomic structure.
• The significant observation that he made was that the characteristics of cathode rays did not depend on the material of the electrodes.
• It is independent of the nature of the gas present in the cathode ray tube. 
• In a nutshell, we came to know that electrons are the basic constituents of all atoms.

The number of electrons dispersed outside the nucleus is equal to the number of positively charged protons present in the nucleus. This also explains the electrically neutral nature of an atom.

Uses of Cathode Ray Tube

The uses of cathode ray tubes are as follows:

• Cathode ray tubes are used in computer monitors used to use CRT technology.
• X-rays are produced with the help of this tube.
• The technology is used in the screen of a cathode ray oscilloscope, which is coated with fluorescent substances. 
• It is used in a video frame on an analogue television set.

Things to Remember

• A cathode ray tube is a vacuum tube which creates a trace on a fluorescent screen due to the presence of electric and magnetic fields.
• They are named after these rays are emitted by the negative electrode.
• Light is produced when electrons hit a fluorescent tube.
• Each cathode ray has similar properties irrespective of the elements.
• It is commercially used in CRT TV production.

Sample Questions

Ques. What are cathode ray tubes made of? (1 mark)

Ans. The cathode is made of a cesium alloy. Cesium is used as a cathode because it releases electrons readily when heated or hit by light.

Ques. Where can you find a cathode ray tube? (2 marks)

Ans. Cathode rays are electron streams observed in vacuum tubes (also known as an electron beam or an e-beam). If an evacuated tube of glass is fitted with two electrodes and a voltage is added, it is found that the glass opposite to the negative electrode glows from the electrons emitted by the cathode.

Ques. How did JJ Thomson find the electron? (2 marks)

Ans. In the year 1897 J.J. Thomson invented the electron by playing with a tube that was Crookes, or cathode ray. He proved that the cathode rays were charged negatively. Thomson understood that the accepted model of an atom did not account for the particles charged positively or negatively.

Ques. What are the properties of cathode rays? (3 marks)

Ans. The properties of cathode rays are as follows:

• Cathode rays move in a straight line and are able to cast sharp shadows.
• Magnetic field and electric field deflect these rays.
• They are produced at the cathode (negatively charged electrode) and travel towards the anode (positively charged electrode) in a vacuum tube.
• The properties of the cathode rays do not depend on the electrodes and the gas used in the vacuum tube.
• Speed of these rays is comparatively slower than light.
• They can penetrate through thin metal plates.
• Phosphors glow if cathode rays fall on it.

Ques. What do you mean by cathode? (2 marks)

Ans. A device’s anode is that terminal through which current flows in from outside. A device’s cathode is its terminal through which current flows out. Electrons are charged negatively, positive current flowing in is the same as out flowing electrons.

Ques. Who discovered the cathode rays? (2 marks)

Ans. In the year 1858, Plücker discovered cathode rays by sealing a couple of electrodes inside the tube, evacuating the air and forcing it between the electric current of the electrode. Cathode rays are negatively charged. They are 180 o  times lighter than hydrogen, the lightest element.

Ques. What is the Colour of cathode rays? (2 marks)

Ans. Cathode-ray tube (CRT), vacuum tube which produces images when electron beams strike its phosphorescent surface. CRTs can be coloured (using usually three electron guns to produce red, green, and blue images that render a multicoloured image when combined) or monochrome (using one electron gun).

Ques. How are cathode rays formed? (2 marks)

Ans. Cathode rays come from the cathode, as the cathode is negatively charged. The rays strike and ionize the gas sample inside the container. The electrons ejected from gas ionization travel to the anode. These rays are electrons that are actually created from the gas ionization inside the tube.

Ques. What are the components used in the cathode ray discharge tube? (4 marks)

Ans. The components used in the cathode ray discharge tube are as follows:

• A focused electron beam is produced by the electron gun or heater.
• Electrons are accelerated by anodes.
• The direction of the electron beam can be continually changed because to the extremely low-frequency electromagnetic field produced by deflecting coils.
• There are two varieties of deflecting coils: vertical and horizontal.
• It is possible to change the beam's intensity.
• A tiny, brilliant visible spot appears on the fluorescent screen as the electron beam strikes the phosphor-coated screen.

Ques. What are the observations of cathode ray experiment? (3 marks)

Ans. The observations of cathode ray experiment are as follows:

• Cathode rays moves from cathode terminal to anode terminal of the battery.
• It travel in a straight line in absence of electric and magnetic field but get deflected in presence of these fields.
• The rays are observed with the help of fluorescent screens.
• The direction of negative rays indicate that these rays are negatively charged.

Ques. What was the result of the cathode ray discharge tube exper­iment? (3 marks)

Ans. The result of the cathode ray discharge tube exper­iment are as follows:

The type of gas in the tube has no bearing on the mass and charge of cathode rays. Electrons are negatively charged particles found in cathode rays. It was determined that every atom had electrons since every gas emits cathode rays.

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3. comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements., 4. name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number., 5. which of the following compounds would undergo aldol condensation, which the cannizzaro reaction and which neither write the structures of the expected products of aldol condensation and cannizzaro reaction.  \((i) methanal \) \((ii) 2-methylpentanal \) \((iii) benzaldehyde \) \((iv) benzophenone \) \((v) cyclohexanone \) \((vi) 1-phenylpropanone \) \((vii) phenylacetaldehyde \) \((viii) butan-1-ol \) \((ix) 2, 2-dimethylbutanal\), 6. give the iupac names of the following compounds: (i)ch 3 ch(cl)ch(br)ch 3 (ii)chf 2 cbrclf (iii)clch 2 c≡cch 2 br (iv)(ccl3) 3 ccl (v)ch 3 c(p-clc 6 h 4 ) 2 ch(br)ch 3 (vi)(ch 3 ) 3 cch=cclc 6 h 4 i-p, subscribe to our news letter.

• Structure of Atom

Canal Ray Experiment

Canal Ray experiment is the experiment performed by German scientist Eugen Goldstein that led to the discovery of the proton. The discovery of proton which happened after the discovery of the electron further strengthened the structure of the atom . In the experiment, Goldstein applied high voltage across a discharge tube which had a perforated cathode. A faint luminous ray was seen extending from the holes in the back of the cathode.

Table of Contents

Apparatus of the experiment, procedure of the experiment, explanation, frequently asked questions – faqs.

The apparatus of the experiment incorporates the same apparatus as of cathode ray experiment which is made up of a glass tube containing two pieces of metals ions at the different end which acts as an electrode. The two metal pieces are connected with an external voltage. The pressure of the gas inside the tube is lowered by evacuating the air.

• Apparatus was set up by providing a high voltage source and evacuating the air to maintain low pressure inside the tube.
• High voltage was passed to the two metal pieces to ionise the air and make it a conductor of electricity.
• The electricity started flowing as the circuit was complete.
• When the voltage was increased to several thousand volts, a faint luminous ray was seen extending from the holes in the back of the cathode.
• These rays were moving in the opposite direction of cathode rays and were named canal rays.

When very high voltage is applied, it ionises the gas and it is positive ions of gas that constitutes the canal ray. It is actually the nucleus or kernel of the gas that was used in the tube and hence it has properties different from the cathode rays which were made up of electrons.

• Unlike cathode rays, canal rays depend upon the nature of gas present in the tube. It is because the canal rays are composed of positive ionised ions formed by ionisation of gas present in the tube.
• The charge to mass ratio for the particles of the ray was found to be different for different gases.
• The behaviour of particles in an electric and magnetic field was opposite to that of cathode rays.
• Some positively charged particles carry multiples of the fundamental value of the charge.

Who discovered the canal rays?

Dempster was one of the first spectrometers to use such sources of ions. He never succeeded in using magnetic bending. By the light, they released while travelling through gases and by the fluorescent patch they created on the discharge tube wall, Goldstein had discovered canal rays.

Why anode rays are called canal rays?

These rays are particle beams that travel in a direction opposite to the “cathode rays,” which are electron waves that move through the anode. These were called canal rays because they passed through the holes or canals in the cathode

What was Goldstein experiment?

In the 1870s, Goldstein conducted his own discharge tube experiments and named Kathodenstrahlen, or cathode rays, the light emissions examined by others. He found some major cathode ray properties, which led to their subsequent discovery as the electron, the first subatomic particle.

What is the difference between cathode rays and canal rays?

Cathode rays are charged negatively, while Canal Rays are charged positively. Cathode rays emanate from the cathode, while the rays of the canal do not emanate from the anode, but are produced inside the chamber by the collision of gas molecules. In an electric field, cathode rays are drawn to positive electrodes.

How canal rays are produced?

The electrons emitted from the cathode collide with the gas atoms found in the tube, knocking one or two additional electrons out of each of these atoms. These collisions leave behind ions which are positively charged. The produced positive ions travel towards the cathode. Any of the positive ions pass through the perforations that create canal rays in the cathode disc. Both electric and magnetic fields deflect the channel rays in the same direction from the cathode rays.

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Describe J.J Thomsons experiment on the discovery of cathode rays.

J.j thomson’s and others conducted an experiment to a vacuum pump. metal electrodes are fitted to the ends of the glass tube, as shown in the figure. he created very low pressure inside the discharge tube and applied high voltage. he observed a greenish glow near the anode of the glass tube. the rays which are emitted from the cathode hit the anode and cause the greenish glow. the streams of rays emitted from the cathode are called cathode rays. which are made of small particles he called electrons.

State the postulates of daltons atomic theory ?

Describe JJ Thomson experiments on discovery of electrons .

List out the characters of anode rays.

Describe Rutherford model of an atom

Describe the properties of cathode rays

State the conclusion drawn by Alpha ray scattering experiment of Rutherford

With respect to the discovery Of electron- cathode ray experiment, answer the following questions. (a) Who discovered cathode rays ? (b) Describe the experimental set up. (c) Define cathode rays. (d) Draw a neat and labelled diagram of cathode ray experiment.

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• Published: 04 September 2024

Frequency ratio of the 229m Th nuclear isomeric transition and the 87 Sr atomic clock

• Chuankun Zhang   ORCID: orcid.org/0000-0001-5669-9082 1 , 2 , 3 ,
• Tian Ooi   ORCID: orcid.org/0009-0004-2738-0186 1 , 2 , 3 ,
• Jacob S. Higgins 1 , 2 , 3 ,
• Jack F. Doyle 1 , 2 , 3 ,
• Lars von der Wense 1 , 2 , 3   nAff7 ,
• Kjeld Beeks   ORCID: orcid.org/0000-0002-8707-6723 4   nAff8 ,
• Adrian Leitner   ORCID: orcid.org/0009-0007-1156-1881 4 ,
• Georgy A. Kazakov 4 ,
• Peng Li 5 ,
• Peter G. Thirolf 6 ,
• Thorsten Schumm   ORCID: orcid.org/0000-0002-1066-202X 4 &
• Jun Ye   ORCID: orcid.org/0000-0003-0076-2112 1 , 2 , 3  

Nature volume  633 ,  pages 63–70 ( 2024 ) Cite this article

Metrics details

• Atomic and molecular physics
• Nuclear physics
• Optical physics
• Quantum physics

Optical atomic clocks 1 , 2 use electronic energy levels to precisely keep track of time. A clock based on nuclear energy levels promises a next-generation platform for precision metrology and fundamental physics studies. Thorium-229 nuclei exhibit a uniquely low-energy nuclear transition within reach of state-of-the-art vacuum ultraviolet (VUV) laser light sources and have, therefore, been proposed for construction of a nuclear clock 3 , 4 . However, quantum-state-resolved spectroscopy of the 229m Th isomer to determine the underlying nuclear structure and establish a direct frequency connection with existing atomic clocks has yet to be performed. Here, we use a VUV frequency comb to directly excite the narrow 229 Th nuclear clock transition in a solid-state CaF 2 host material and determine the absolute transition frequency. We stabilize the fundamental frequency comb to the JILA 87 Sr clock 2 and coherently upconvert the fundamental to its seventh harmonic in the VUV range by using a femtosecond enhancement cavity. This VUV comb establishes a frequency link between nuclear and electronic energy levels and allows us to directly measure the frequency ratio of the 229 Th nuclear clock transition and the 87 Sr atomic clock. We also precisely measure the nuclear quadrupole splittings and extract intrinsic properties of the isomer. These results mark the start of nuclear-based solid-state optical clocks and demonstrate the first comparison, to our knowledge, of nuclear and atomic clocks for fundamental physics studies. This work represents a confluence of precision metrology, ultrafast strong-field physics, nuclear physics and fundamental physics.

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Acknowledgements

We thank K. Kim, A. Aeppli, W. Warfield and W. Milner for building and maintaining the JILA 87 Sr optical clock; D. Lee, Z. Hu and B. Lewis for building and maintaining the JILA stable laser and the cryogenic Si cavity; the entire crystal growth team at TU Wien for preparation of the thorium-doped crystal; M. E. Fermann and J. Jiang for help in constructing the high-power infrared frequency comb; K. Hagen, C. Schwadron, K. Thatcher, H. Green, D. Warren and J. Uhrich for help in designing and building mechanical parts used in the detection setup; T. Brown and I. Rýger for help in designing and making electronics used in the experiment; M. Ashton, B. C. Denton and M. R. Statham for help in the shipment of radioactive samples; E. Hudson, E. Peik, J. Hur, J. Thompson, J. Weitenberg and A. Ozawa for helpful discussions; and IMRA America for collaboration. We acknowledge funding support from the Army Research Office (grant no. W911NF2010182), the Air Force Office of Scientific Research (grant no. FA9550-19-1-0148), the National Science Foundation (grant no. QLCI OMA-2016244), the National Science Foundation (grant no. PHY-2317149) and the National Institute of Standards and Technology. J.S.H. acknowledges support from a National Research Council Postdoctoral Fellowship. L.v.d.W. acknowledges funding from a Feodor Lynen fellowship from the Humboldt Foundation. P.G.T. acknowledges support from the European Research Council (Horizon 2020, grant no. 856415) and the European Union’s Horizon 2020 Programme (grant no. 664732). The 229 Th:CaF 2 crystal was grown in TU Wien with support from the European Research Council (Horizon 2020, grant no. 856415) and the Austrian Science Fund (grant DOI: 10.55776/F1004, 10.55776/J4834 and 10.55776/ PIN9526523). The project 23FUN03 HIOC (grant DOI: 10.13039/100019599) has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the participating states. We thank the National Isotope Development Center of DoE and Oak Ridge National Laboratory for providing the Th-229 used in this work.

Author information

Lars von der Wense

Present address: Johannes Gutenberg-Universität Mainz, Institut für Physik, Mainz, Germany

Kjeld Beeks

Present address: Laboratory for Ultrafast Microscopy and Electron Scattering (LUMES), Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland

Authors and Affiliations

JILA, University of Colorado Boulder, Boulder, CO, USA

Chuankun Zhang, Tian Ooi, Jacob S. Higgins, Jack F. Doyle, Lars von der Wense & Jun Ye

NIST, Boulder, CO, USA

Department of Physics, University of Colorado Boulder, Boulder, CO, USA

Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Vienna, Austria

Kjeld Beeks, Adrian Leitner, Georgy A. Kazakov & Thorsten Schumm

IMRA America, Ann Arbor, MI, USA

Ludwig-Maximilians-Universität München, Garching, Germany

Peter G. Thirolf

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Contributions

C.Z., T.O., J.S.H., J.F.D., L.v.d.W., K.B., T.S. and J.Y. conceived and planned the experiment; K.B., A.L., G.A.K. and T.S. grew the thorium-doped crystal and characterized its performance; P.G.T. provided valuable insight and the parabolic mirror; and C.Z., T.O., J.S.H., J.F.D., L.v.d.W., P.L. and J.Y. performed the measurement and analysed the data. All authors wrote the manuscript.

Corresponding authors

Correspondence to Chuankun Zhang or Jun Ye .

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Extended data figures and tables

Extended data fig. 1 locking scheme used in our experimental setup..

A Yb-fiber oscillator is used to generate the fundamental frequency comb 40 . The light is amplified using a chirped pulse amplification scheme in a large mode area gain fiber. The output comb light (average power 40–50 W) is coupled to a femtosecond enhancement cavity with finesse ~600 to further enhance the peak power for efficient cavity-enhanced high harmonic generation. The 7 th harmonic is outcoupled using a grazing incidence plate 42 , 43 (GIP) and directed to the sample chamber. A portion of the pre-amplified comb light is picked off and focused to a highly nonlinear photonic crystal fiber (HNL PCF) for broadband supercontinuum generation. The light is also doubled using a periodically poled lithium niobate (PPLN) crystal. These two beams generate a beatnote that directly reports on f CEO ( f–2   f detection), which can be fed back to the pump current for f CEO locking. The supercontinuum light is beatnote locked against the Sr clock light at 698 nm through an auxiliary narrow linewidth Mephisto laser at 1064 nm. The beatnote  f beat is mixed with a DDS output and is used to steer the Mephisto laser frequency. The Mephisto output is passed through a fiber acousto-optic modulator (AOM) to generate a frequency offset and is beat against a portion of the preamplified fundamental comb light. The control signal is fed back to the oscillator cavity length to close the loop for the f beat lock. We conduct our scans by changing the DDS offset frequency, which ultimately changes the comb repetition frequency without shifting f CEO . An additional portion of the Mephisto light is picked off and modulated with an electro-optical modulator (EOM) for Pound-Drever-Hall locking of the enhancement cavity. The offset between the locked cavity resonance and the fundamental frequency comb can be tuned by adjusting the AOM offset frequency to mitigate intracavity plasma instabilities 56 , 57 . PZT, piezo-electric actuator.

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Zhang, C., Ooi, T., Higgins, J.S. et al. Frequency ratio of the 229m Th nuclear isomeric transition and the 87 Sr atomic clock. Nature 633 , 63–70 (2024). https://doi.org/10.1038/s41586-024-07839-6

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Received : 20 June 2024

Accepted : 17 July 2024

Published : 04 September 2024

Issue Date : 05 September 2024

DOI : https://doi.org/10.1038/s41586-024-07839-6

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