HRRL OTR Test Mar 3rd 2011
Preparation
JAI Camera Setup
Target in:
Target out:
Target in after shielded:
Objectives
Determined if the steering magnets of the gun are connected to power supply
1. Physically check looking at wires.
2. Change currents on the steering magnet, and observe position of the beam spot. If changes then, connected.
Tune beam using Linac optics only
Chad will tune up the beam using steering elements which are within the HRRL Linac only.
Determined if the OTR target is centered on the beam line
With all beam line magnets off, observe the beam spot at the OTR target. If the beam is centered on the OTR target, then OTR target MAY be centered on the beam line.
Polarization test
Insert a polarizer film. Take several picture for different orientations without changing beam properties.
Angel is measured with respect to:
| Polarizer Angel | Iamge |
| 200 px | 200 px |
Determined if the quads are centered on the beam line
The power supplies for ALL quads should be off.
Turn on Quad closesst to HRRL
If the beam deflects, try to align quad so there is no deflection
Turn on Quad closest to OTR target
If the beam deflects, try to align quad so there is no deflection
Run
Field Emission Check
Peak Current (mA): 160
Rep Rate (Hz): 6
Pulse width (ns): 200
HV on, Filament on, RF on
HV off, Filament on, RF on
HV off, Filament on, RF off
HV on, Filament on, RF off
HV on, Filament on, RF on, Valve closed
HV off, Filament on, RF on, Valve closed
HV on, Filament on, RF off, Valve closed
HV off, Filament on, RF off, Valve closed
Conclusion
When the HV is off, there were not any electrons from filament. We still see back ground light. This light was gone when the RF was turned off or vacuum valve (between screen and gun) was closed. So, this back ground light was due the the dark current that emitted from the cavity (field emission).
Estimation of How Much off
Rep Rate (Hz): 6
Pulse width (ns): 200
Take at least 3 images for each setting below.
The goal is to estimate how far things may be misaligned. Several assumption will be made.
Tuned for Max transmision to FC Just by steering Magnets
Peak Current (mA): 160
Tuned for Max transmision to FC by using quads and steering Magnets
Using 1st Triplets
Peak Current (mA): 160
Using 2nd Triplets
Peak Current (mA): 160
Using Both Triplets
Peak Current (mA): 160
Tuned for Min Quad deflection
Find the spot that when we change quad currents, center of the beam spot does not change or change the lest.
Rep Rate (Hz): 6
Pulse width (ns): 200
Quqads off
Peak Current (mA): 35
Quads off:
1st quad of the 1st triplet on
1st quad of the 1st triplet power supply at (A): 2
1st quad of the 1st triplet power supply at (A): 4
1st quad of the 1st triplet power supply at (A): 6
1st quad of the 1st triplet power supply at (A): 8
1st quad of the 1st triplet power supply at (A): 10
2nd quad of the 1st triplet on
2nd quad of the 1st triplet power supply at (A): 2
2nd quad of the 1st triplet power supply at (A): 4
2nd quad of the 1st triplet power supply at (A): 6
2nd quad of the 1st triplet power supply at (A): 8
2nd quad of the 1st triplet power supply at (A): 10
Tune on center of Target
Rep Rate (Hz): 6 Pulse width (ns): 200 Peak Current (mA): 120
Tuned on center of the target:
Rf on, HV off (for back ground subtraction):
No beam, light is on:
OTR Check Polarization
Pulse width (FMHM): 200 ns
Peak Current: 160 mA
Camera focused at infinity.
No polarizer
Accelerator off, back ground
50 Hz Rep Rate
291 Hz Rep Rate
Polarization of the Polarizer Parallel to the Beam Line Direction
Polarization of the Polarizer Perpendicular to the Beam Line Direction
Time Slice Study of the OTR
Take pictures at different time slices from the trigger.
This means take a picture and then delay the trigger pulse to the camera relative to the RF. Perhaps the light has a time structure.
Rep Rate (Hz): 6
Pulse width (ns): 200
160 mA peak Current
Peak Current (mA): 160
105 mA peak Current
Peak Current (mA): 105
Far field
Now return the camera trigger back to the original location in time. Focus at infinity and try to observe polarization.
Report
Field Emission
When the HV is off, there were not any electrons from filament. We still see back ground light. This light was gone when the RF was turned off or vacuum valve (between screen and gun) was closed. So, this back ground light was due the the dark current that emitted from the cavity (field emission).
Beam Alignment
The center of the target, the beam spot has maximum transmision to FC, and min quad deflection beam spot are at different positions. Thus, beam line is not aliened.
Back to Positrons