Hollow electron gun CHG-16-sc¶
- Table of contents
- Hollow electron gun CHG-16-sc
This is a hollow electron gun prototype for collimation and scraping in the High-Luminosity Large Hadron Collider (HL-LHC).
|Assembled electron gun|
- scandate cathode for higher current densities
- smaller inner and outer cathode diameters, 8 mm and 16 mm, to better match the dimensions of the LHC proton beam halo
- scaled electrode distances and dimensions to preserve same perveance as the CHG1 e-gun
The 16-mm scandate cathode¶
The cathode was manufactured at the Beijing Vacuum Electronics Research Institute (BVERI).
|Cathode in transport case||Upright cathode||Detail of emitting surface||Detail of filament connections|
Operating instructions from manufacturer [PDF]
Electron emission was simulated with the Warp particle-in-cell code.
Here is an example at 10 kV, 0.4 T, 6.91 A:
|Overview [PDF]||Current vs. z [PDF]||Current-density vs. radius [PDF] [data]|
Particle positions and velocities for a few cases can be found in the following table.Each data table has 8 columns:
- macroparticle number
- x, y, z coordinates [m]
- vx, vy, vz velocity components [m/s]
- macroparticle weight
|0.5 kV, 0.4 T, 78 mA||Data|
|10 kV, 0.4 T, 6.91 A||Data|
Yield vs. voltage and perveance¶
|Predicted yield vs. voltage [PDF]|
The predicted perveance is 6.91 uperv.
Emission vs. voltage/current and magnetic field¶
|0.05 T||0.1 T||0.2 T||0.3 T||0.4 T||0.5 T||1.0 T|
|0.5 kV, 78 mA|
|6 kV, 3.22 A|
|10 kV, 6.91 A|
Installation in Fermilab test stand¶
The electron gun was installed in the Fermilab electron-lens test stand on June 5, 2018 to characterize its performance.
Photographs of the installation.
The cathode is heated by controlling the filament current.
|Filament resistance vs. filament current [PDF] [data]||Filament resistance vs. filament power [PDF]|
The filament resistance is an indication of temperature. Above a certain heating power, heating dissipation is mostly radiative.
Temperature distributions and infrared images were taken on Oct. 5, 2018 with filament heater at 5.8 A.
|Temperatures on contact||Infrared image|
Preliminary results are discussed in these slides
After the first conditioning, the current yield was measured as a function of voltage in the Fermilab electron-lens test stand on Oct. 10, 2018.
|Measured current yield vs. voltage [PDF] [data]|
During this test, the electron gun delivered 5.2 A at 10 kV.
At high voltage, the cathode is still temperature limited. Further conditioning is under way to extend space-charge-limited emission up to 10 kV.
Preliminary 1-dimensional scans of the current-density profiles using 4 downstream correctors to check alignment.
|(red = pinhole current; green = vacuum monitor)|
First 2D profiles at 0.5 kV, 83 mA at 3.5-4-1 kG solenoid configuration.