H0 H- BEAM CURRENT MONITOR
HALF SECTOR TEST 22 – 03 - 2017
Araceli Navarro, Federico Roncarolo
BI - PM
H0 H- PLATES
• 4 Titanium plates, 1 mm thick.
• To
measure
non
stripped
H0/H• Placed
inside
the
BSW4
Chamber
• Monitor
at
4cm
from
the
3
dump.
LIST OF MEASUREMENTS
• 7 March 2017:
• 7 mA beam. No measure of the last plate. First 3 measurements with Steerer, other 3 with
BSW3/BSW4.
• 9 March 2017:
• First try with a pencil beam. Beam was not good enough. We manage to put the beam on H-R
only.
• 13 March 2017:
• 0.6 mA beam . Measurement of all the plates. All measurements with BSW3/BSW4.
• 6 mA beam. Measurement of all the plates. All measurements with BSW3/BSW4.
• 15 March 2017:
• 7.2 mA beam. Test effect of different polarizations in H0/H- plates. Not change observed.
• 17 March 2017:
• 8.1 mA beam. All measurements with BSW3/BSW4. Reconstruction of the beam profile with H0L
plate.
• 20 March 2017:
• 0.6 mA beam. All measurements with BSW3/BSW4. And all measurements with BSW4 fixed.
• Study of the beam evolution along the four plates.
3
MEASUREMENT PROCEDURE
• Scan a ‘small as possible’ from left to right, stopping when it is on 1 single plate
or equally split on two plates
• Analysis so-far based on OASIS traces
• VME digitized data (logged) to be analyzed
H0
L
1
H0
R
2
3
HM
R
HM
L
4
5
6
7
4
RESULTS SO FAR
Scanning the beam either using an upstream steerer or BSW3 and BSW4 at
the same time
• H- plates give higher signal than H0
plates (not in all cases)
• Effect of gap between plates
• Secondary Emission effect ?
• Do magnets interfere in the
measurements?
• Do we have losses while steering?
5
Effect of secondary emission
• Secondary Emission (SE) can deteriorate
signal (which is meant to be due to the
stripped electrons deposition in the plates)
• SEY H- in titanium ~ 0.0766 /𝐻−
• BSW4 field expected to suppress SE
• SE have very low energy << 100eV
• Bias of the plates (possible between +30V) can also partially affect SE
• Plot on the right:
• reference trace +30V.
• Measurement -30V.
• No evident effect of bias
15 March: BSW off. 8.4mA Beam in H0L with Steerer.
6
SCAN WITH BSW3 AND BSW4
SCAN WITH ONLY BSW3
(BSW4 at constant current)
• Left: 0.6 mA Beam. Steered with
both BSW3 and BSW4
• Right: 0.6 mA Beam. Steered only
with BSW3. BSW4 fixed to 3094 A
• Influence of magnetic field in the
SE.
7
SUMMARY (I)
• We’ve measured the response of the plates for different
intensities.
• 7.6 mA, 8.1 mA, 6 mA, 2 x 0.6 mA.
• Results are not conclusive.
• More data is needed, preferably for lower intensities.
• Steering with only BSW3 (only one set of meas.) would indicate
that BSW4 magnetic field has an influence in the measurement
• Need to repeat measurements with other intensities to
confirm this
9
SUMMARY (II)
Digitized data via VME (operational system for PSB!)
• Analysis of logged data with first card version
• First card heavily affected by EMI noise/background -> surely not suitable for
interlock channel
• Second card being tested since yesterday
• Looks more sensible (higher signal to noise) and less affected by EMI
• Grounding of connectors not optimal (assembly or design fault, to be studied)
• Present manual fix (maybe fragile): to be checked if allows studying interlock
channel
• If we can make it working, need at least to re-do all measurements done with
first card
• In general:
• would be essential to have final calibration measurements with ‘pencil’ and
characterized beam at different intensities (mA, possibly pulse length for
interlock and 50ns mode)
 correlate plates data to known beam size, intensity, be sure of no losses
while steering and no leakage between plates (beam halo)
9