1. Vertical Beam Halo Study using Diamond Sensor. June 2015 ATF2
V. Kubytskyi, H. Guler, P. Bambade,
ATF team
20/06/2015

2. Shifts Fri 5/29 Diamond Sensor
Tue 6/9
Thu 6/11
YAG screen/ Diamond Sensor
Wed 6/17
Fri 6/19
YAG screen/Diamond Sensor

3. 1.3 Signals measured at ATF2
Total charge in the diamond
50 V
200 V
400 V
BEAM
Ch1
Ch2
Ch3
Ch4
10 waveforms at each position
ch1
ch2
ch3
ch4

4. Scan procedure
First Beam core V with 30dB attenuators. Find the beam position.
Beam steering (horiz/vert) to maximize signal on given channel.
Beam core V with 30dB attenuators. Fitting each channel to obtain sigma and position.
Move DS far from beam core. Remove attenuators.
Scan left beam V; BEAM OFF; move to the right; BEAM ON; Scan right beam V
~ 300 Scans, 5-7 min on average
About 11 Gb of data for postprocessing. Data for Beam cores and beam halos need to be combined.

5. Data analysis. Postprocessing.

6. Role on the vertical beam halo of:
Collimator
Vacuum level (4.84e-7 Pa;   9.8e-7 Pa; 1.35e-6 Pa)
Intensity
And
Additional characterization of our DS: charge collection by individual electrodes; step termination of charge collection; …

7. Vertical Beam halo scan. N ≈ 8e9
Red: 10x1 optics, σ= 1.46 mm
Blue: 10x4 optics, σ=0.98 mm
Determined the cut by the BDUMP aperture.

8. Investigated role of collimator on the beam halo cut
Investigated role of collimator on the beam halo cut. 0.1mm of collimator displacement-> 0.5mm halo cut position.
Limited range of collimator positions-> Observed effect only on the left side of halo (top side).
Role of Collimator
Cut from BDUMP aperture
zoom
Cuts from collimator

9. Displace the beam using Y shift on QD0FF from 300 mum to -1300 mum
Cut from BDUMP aperture
Cut from collimator

10. Vacuum level
Vertical scan. N ≈ 8e9 (for better detection of halo)
First complete scan of beam core and beam halo (red).
Turned on ion pumps, vacuum level recovered quickly (5~10mins) to 4.4e-7.
Second complete scan of beam core and beam halo (blue).
Zoom of the beam core
Rough estimation:
Vacuum changed≈2 times
and Halo changed ≈2 times
Sigma CH1-CH4: mm

11. Vacuum level
Zoom of the beam core
Red e-7 Pa
Black  13.5e-7 Pa
SigmaCH1-4:

12. Charge collection by different channels. N = 3e9
Small variation in Sigma 4 1
CH1 1
CH2
CH3
CH4
Plugged channel: 1
In air : 0

13. Problems/difficulties and future improvements
Possibilities decrease pickup?
After long DS operation at -400V the power supply started to provide large current… Fortunately with Keithley PS we can monitor it. The cause could be in the behavior of capacitors after long operation/irradiation… After 5 hours system is recovered.
Vertical motor homing, brakes – controller software problem. Sometimes working/not working.
Patch panel for the signal cables is hardly accessible. Difficult to insert/remove attenuators. 17/06 we removed it.

14. Temperature measurements
Pt100 not plugged : PT100 : / / degC PT100 : / / degC PT100 : / / degC Plugged: PT100 : / / degC

15. Backup

16. Some improvements
Added software communication with Keithley 2410 power supply.
New algorithm for automatic determination of the best vertical range for the scope.
Pdf report generator (waveforms, parameters…)

17. Horizontal scan. N = 2e9; Vacuum =7.87e-7
Beam core scan, beam steering, vertical alignment.
Complete scan of beam core and beam halo:
Sigmas CH1-CH4: mm

18. Nonlinear regime of charge collection
Predicted from the modelling step-like behavior in a waveform at the end of charge collection.
Difficult to measure with 8-bit scope

19. 1.1 What is diamond sensor? Diamond 1 MIP≈36 in 1 μm High Voltage
Introduction to DS
1.1 What is diamond sensor?
d=500μm
1 MIP≈ in 1 μm
High Voltage
400 V
Reading side
0 V
Diamond
E = V/d