Enter a player name to begin or load your saved progress.
Secondary emission is defined as the phenomenon wherein incident primary particles, upon striking a surface or passing through a substance, induce the emission of secondary particles.
Answer: True
Explanation: This process involves the transfer of energy from incident particles to the material, leading to the ejection of secondary particles, which can be electrons, ions, or atoms.
The secondary emission yield quantifies the ratio of emitted secondary particles relative to the number of incident primary particles.
Answer: True
Explanation: The secondary emission yield is defined as the ratio of the number of secondary particles emitted to the number of primary incident particles. A yield greater than one indicates amplification.
When primary particles cause the emission of ions, the phenomenon is called secondary electron emission.
Answer: False
Explanation: The emission of secondary particles that are ions is specifically termed secondary ion emission. Secondary electron emission refers to the emission of electrons.
Secondary electron emission and secondary ion emission are fundamentally the same process, just involving different particle types.
Answer: False
Explanation: While both are forms of secondary emission triggered by primary particle impact, the underlying mechanisms and resulting particle types (electrons vs. ions) differ significantly, influencing their behavior and applications.
The secondary emission yield measures the ratio of emitted secondary particles to incident primary particles.
Answer: True
Explanation: This ratio is the standard definition of secondary emission yield, indicating the efficiency of particle emission per incident particle. A yield greater than unity signifies electron multiplication.
Based on the provided material, what is the fundamental definition of secondary emission?
Answer: The release of secondary particles caused by the impact of primary particles on a surface or substance.
Explanation: Secondary emission is defined as the emission of secondary particles from a surface or substance due to bombardment by incident primary particles, such as electrons, ions, or photons.
What metric quantifies the efficiency of secondary electron emission?
Answer: Secondary emission yield
Explanation: The secondary emission yield is the standard measure used to quantify the efficiency of secondary electron emission, representing the ratio of emitted secondary electrons to incident primary particles.
What term is used when the secondary particles emitted due to primary particle impact are ions?
Answer: Secondary ion emission
Explanation: When the secondary particles ejected from a surface due to primary particle bombardment are ions, the phenomenon is specifically referred to as secondary ion emission.
What is the key difference between secondary electron emission and secondary ion emission?
Answer: The nature of the secondary particles emitted (electrons vs. ions).
Explanation: The fundamental distinction lies in the identity of the ejected particles: secondary electron emission involves the release of electrons, whereas secondary ion emission involves the release of ions.
The secondary emission yield is defined as the ratio of:
Answer: Secondary particles emitted to primary particles incident.
Explanation: The secondary emission yield is formally defined as the ratio of the number of secondary particles emitted from a surface to the number of primary particles incident upon that surface.
Photomultiplier tubes and image intensifier tubes utilize secondary electron emission to amplify weak initial signals.
Answer: True
Explanation: These devices leverage secondary electron emission to achieve significant signal amplification. Incident photons or particles generate initial electrons, which then trigger a cascade of secondary electrons through multiple stages, resulting in a measurable output current.
In a photomultiplier tube, secondary emission is used to decrease the signal strength.
Answer: False
Explanation: Secondary emission is employed in photomultiplier tubes precisely to amplify, not decrease, the signal strength. The cascading effect through dynodes multiplies the initial signal.
In a photomultiplier tube, secondary emission is used to amplify the initial signal by causing multiple electrons to be emitted from dynodes for each incident electron.
Answer: True
Explanation: This cascading process, where each incident electron liberates multiple secondary electrons from successive dynodes, is the fundamental mechanism for signal amplification in photomultiplier tubes.
Electron multipliers are devices that use secondary emission principles for detecting fast particles like electrons and ions.
Answer: True
Explanation: Electron multipliers, similar in principle to photomultiplier tubes but often designed for different particle types, employ secondary emission to detect and amplify signals from incident electrons, ions, and other energetic particles.
The diagram of a photomultiplier tube shows secondary emission occurring at the photocathode.
Answer: False
Explanation: In a photomultiplier tube, the photocathode is responsible for the initial photoemission (converting light into electrons). Secondary emission occurs subsequently at the dynodes, where these initial electrons are multiplied.
Secondary emission is primarily relevant in applied physics, with little significance in basic research.
Answer: False
Explanation: Secondary emission is significant in both basic research, for understanding surface interactions and material properties, and in applied physics, for the development of sensitive detectors and electronic devices.
The dynode in multiplier tubes serves as the surface that emits secondary electrons when struck by primary electrons.
Answer: True
Explanation: Dynodes are specifically designed electrodes within multiplier tubes that, when bombarded by energetic primary electrons, release multiple secondary electrons, thereby amplifying the signal.
The cascaded dynode chain in a photomultiplier tube typically provides a multiplication gain of around one hundred.
Answer: False
Explanation: The cascaded dynode structure in a photomultiplier tube typically achieves a much higher multiplication gain, often on the order of one million, due to the cumulative effect of secondary emission at each stage.
Which of the following devices uses secondary electron emission for signal amplification?
Answer: Photomultiplier tube
Explanation: Photomultiplier tubes are prime examples of devices that utilize secondary electron emission from their dynode stages to amplify extremely weak initial signals, such as those generated by incident photons.
How does secondary emission contribute to the function of a photomultiplier tube?
Answer: It amplifies the initial signal by causing multiple electrons to be emitted from dynodes for each incident electron.
Explanation: The core function of secondary emission in a photomultiplier tube is signal amplification. Incident electrons strike dynodes, releasing multiple secondary electrons, which then cascade through subsequent dynodes, multiplying the signal significantly.
What is the primary function of the dynodes in a photomultiplier tube?
Answer: To release multiple secondary electrons when struck by a primary electron, amplifying the signal.
Explanation: Dynodes are designed to exhibit a high secondary emission yield. When struck by an electron, each dynode emits several secondary electrons, initiating and sustaining the electron multiplication cascade essential for signal amplification.
Electron multipliers are mentioned as devices that utilize secondary emission for what purpose?
Answer: Detecting fast particles like electrons and ions
Explanation: Electron multipliers employ secondary emission to amplify the signal generated by the detection of fast-moving particles, such as electrons and ions, making them suitable for various detection applications.
Within the context of tubes like photomultipliers, what is the function of the dynode?
Answer: To emit multiple secondary electrons when hit by an incoming electron.
Explanation: The dynode serves as an electron multiplication stage. When struck by an incident electron, it releases several secondary electrons, thereby amplifying the signal in a cascading process.
What is the typical order of magnitude for the electron multiplication gain achieved through the cascaded dynodes in a photomultiplier tube?
Answer: One million
Explanation: Through the successive stages of secondary emission in a cascaded dynode chain, photomultiplier tubes can achieve substantial signal amplification, typically resulting in a total gain on the order of one million.
In the context of vacuum tubes, secondary emission almost exclusively refers to the emission of ions.
Answer: False
Explanation: While secondary emission can involve ions, in the context of vacuum tubes, it most commonly refers to the emission of secondary electrons from surfaces struck by primary electrons or ions.
Undesirable parasitic oscillations in electronic vacuum tubes can sometimes be caused by secondary emission.
Answer: True
Explanation: Secondary emission, particularly from the anode or grid structures, can lead to complex current flows and feedback mechanisms, potentially resulting in unwanted parasitic oscillations in vacuum tube circuits.
Historically, secondary emission caused the central spot on an oscilloscope screen to appear dimmer.
Answer: False
Explanation: Secondary emission from the screen of a cathode-ray tube could lead to a spreading of the electron impact, causing a disk-like effect or halo around the central spot, rather than simply making it dimmer.
Special amplifying tubes developed in the 1930s used secondary emission to decrease the distance between the plate and grid.
Answer: True
Explanation: These tubes, such as the orbital beam hexode, utilized secondary emission to achieve higher transconductance within a compact physical structure, effectively increasing the plate-grid interaction without physically reducing the distance.
A major advantage of the orbital beam hexode was its exceptionally long operational lifetime.
Answer: False
Explanation: A significant drawback of the orbital beam hexode and similar tubes was their limited operational lifetime, often due to rapid degradation of the dynode surface caused by intense electron currents.
Secondary emission was a desirable characteristic in tetrode vacuum tubes, enhancing their performance.
Answer: False
Explanation: Secondary emission was generally an undesirable effect in tetrode vacuum tubes, often leading to instability and parasitic oscillations. The development of the pentode was a direct response to mitigate these issues.
The negative resistance characteristic caused by secondary emission in some older tubes was sometimes used to create oscillators.
Answer: True
Explanation: The negative resistance phenomenon, arising from secondary emission effects in certain vacuum tube configurations (like dynatrons), was indeed exploited in the design of oscillators.
The addition of a suppressor grid to tetrodes led to the development of the pentode tube and solved secondary emission issues.
Answer: True
Explanation: The introduction of a suppressor grid between the anode and screen grid in tetrodes effectively repelled secondary electrons back to the anode, mitigating the problems associated with secondary emission and leading to the development of the pentode.
The disk-like effect seen at higher intensity on oscilloscope screens is caused by the primary electron beam itself spreading out.
Answer: False
Explanation: The disk-like effect observed at higher intensities on oscilloscope screens is attributed to secondary emission from the screen itself, where dislodged electrons are re-accelerated, spreading the impact area.
Secondary emission from the anode in tetrode tubes was a major problem leading to instability.
Answer: True
Explanation: In tetrodes, electrons accelerated by the screen grid could strike the anode with sufficient energy to cause secondary emission. This phenomenon could lead to excessive current to the screen grid and induce circuit instability.
In the context of vacuum tubes, what type of particle is most commonly implied when discussing secondary emission?
Answer: Secondary electrons
Explanation: While secondary emission can involve ions, in the context of vacuum tubes, the term most frequently refers to secondary electrons emitted from surfaces when struck by primary electrons or other charged particles.
Which of the following is cited as an undesirable effect of secondary emission in vacuum tubes?
Answer: Parasitic oscillations
Explanation: Secondary emission can lead to complex feedback loops and current variations within vacuum tubes, often manifesting as undesirable parasitic oscillations that disrupt normal circuit operation.
Historically, what effect did secondary emission have on the visual representation of the spot on an oscilloscope screen?
Answer: It caused a disk-like effect around the central dot due to re-accelerated secondary electrons.
Explanation: When the electron beam struck the screen with high intensity, secondary electrons were emitted. These were re-accelerated towards the screen, causing the impact area to spread and creating a visible disk-like effect around the primary spot.
What was a key design goal of the special amplifying tubes developed in the 1930s that used secondary emission?
Answer: To increase transconductance and reduce noise figure.
Explanation: These specialized tubes aimed to enhance performance by increasing transconductance (a measure of amplification efficiency) and reducing the noise figure, thereby improving signal-to-noise ratio.
What significant problem limited the operational lifetime of early amplifying tubes like the orbital beam hexode?
Answer: Rapid damage to the dynode surface from intense electron current.
Explanation: The high electron currents and energies involved in the secondary emission process within these tubes could lead to rapid erosion and damage of the dynode surfaces, significantly shortening their operational lifespan.
In which type of thermionic valve did secondary emission cause issues like excessive current to the screen grid?
Answer: Tetrode
Explanation: Tetrode vacuum tubes were particularly susceptible to problems caused by secondary emission from the anode, which could result in excessive current flow to the screen grid and circuit instability.
The negative resistance characteristic, sometimes caused by secondary emission, was utilized in which type of oscillator?
Answer: Dynatron oscillator
Explanation: The negative resistance effect, often a consequence of secondary emission in certain vacuum tube configurations, was specifically employed in the design of dynatron oscillators.
What innovation addressed the problems caused by secondary emission in tetrodes, leading to the development of the pentode?
Answer: Introducing a suppressor grid.
Explanation: The addition of a suppressor grid, typically at cathode potential, effectively repelled secondary electrons back to the anode, mitigating the issues associated with secondary emission and paving the way for the pentode tube.
What was the primary issue secondary emission caused in tetrode vacuum tubes?
Answer: Led to excessive current to the screen grid and potential instability.
Explanation: Secondary electrons emitted from the anode in tetrodes could be collected by the positively biased screen grid, leading to increased screen grid current and potentially causing circuit instability or oscillations.
The Selectron tube, an early computer memory technology, did not rely on secondary emission principles.
Answer: False
Explanation: The Selectron tube, along with the Williams tube, was an early form of random-access memory that utilized secondary emission principles for data storage.
Magnetic-core memory was developed before and led to the obsolescence of the Williams tube.
Answer: False
Explanation: Magnetic-core memory was developed later than the Williams tube and ultimately replaced it, along with other memory tube technologies, due to its greater reliability and capacity.
Which early computer memory technology relied on secondary emission principles?
Answer: Williams tube
Explanation: The Williams tube was an early form of random-access memory that stored digital information by creating patterns of charge on a cathode-ray tube screen, utilizing secondary emission phenomena.
What technology eventually replaced memory tubes like the Williams tube and Selectron tube?
Answer: Magnetic-core memory
Explanation: Magnetic-core memory, offering greater reliability, density, and non-volatility, eventually superseded memory tubes like the Williams tube and Selectron tube in early computing systems.
Beryllium oxide (BeO) and Gallium arsenide phosphide (GaAsP) are examples of materials used for their secondary emissive properties.
Answer: True
Explanation: These materials, among others like alkali antimonides and magnesium oxide, are known for their high secondary emission yields and are utilized in devices requiring efficient electron multiplication.
Which material is listed in the source as being used for its secondary emissive properties?
Answer: Beryllium oxide (BeO)
Explanation: Beryllium oxide (BeO) is explicitly mentioned as one of the materials utilized for its advantageous secondary emissive properties in various electronic applications.