Written: IJDM 05/03/02
Updated: IJDM 12/03/02
Some of the High Voltage settings for the tagger focal plane detector
were altered from their previous values when the tagger focal plane
was retuned on 21 February 2002. In particular, the highest and lowest
voltages on lines 1 and 10 are not the same for all the power supply
boxes. The table below gives the actual values.
Table of Voltages:
Supply 1 2
3 4
5 6
7 8
9 10
A' 950
1100 1150 1200 1250
1300 1350 1400 1450
1500
A 950 1100
1150 1200 1250 1300
1350 1400 1450 1535
B 1000 1100
1150 1200 1250 1300
1350 1400 1450 1537
C 1000 1100
1150 1200 1250 1300
1350 1400 1450 1500
D 1000 1100
1150 1200 1250 1300
1350 1400 1450 1527
D' 1050 1100
1150 1200 1250 1300
1350 1400 1450 1533
E 1050 1100
1150 1200 1250 1300
1350 1400 1450 1500
E' 1050 1100
1150 1200 1250 1300
1350 1400 1450 1500
E'' 950 1100
1150 1200 1250 1300
1350 1400 1450 1500
Photon Energies:
The table below shows the photon energy range for each Power Supply
for a standard setup for unpolarised photons using an 855 MeV
electron beam. You need to switch on several (all) of the
power supplies to cover a wide (full) range of photon energies.
Power Photon
Energies Eg Range
Rel Eg intensity Monitor
Supply
Covered (MeV) (MeV)
(approx)
Section
E''
42.2 - 114.1
71.9
1.000 ( 0.00dB) V
E'
116.5 - 151.8
35.3
0.362 ( -8.82dB) T
E
154.2 - 199.3
45.1
0.274 (-11.24dB) S
D'
201.7 - 276.1
74.4
0.209 (-13.59dB) Q
D
278.5 - 362.3
83.8
0.152 (-16.36dB) O
C
364.7 - 519.4
154.7 0.116
(-18.71dB) M
B
521.6 - 658.3
136.7 0.081
(-21.94dB) I
A
660.2 - 740.2
80.0
0.064 (-23.88dB) E
A'
741.8 - 792.3
50.5
0.057 (-24.88dB) ?
Note:
1. If you switch off some of the lower photon energy
power supplies to run at increased beam currents, the
"OR 16" Messraum scaler monitor has to be connected to the
highest section of the ladder which is still on. This monitor
is the sum of 16 channels divided by ten.
2. For polarised photons, the part of the tagger which counts
at the greatest rate is not necessarily the lowest photon energy
section switched on. You should be careful about the maximum
count rates and put the "OR 16" monitor on the highest counting
section.
3. The maximum counting rates must be kept below 800000 Hz on
the "OR 16" monitor and below 1000000 Hz on any single channel
(see the 352 individual tagger scalers in the data collected).
4. The February 2002 beamtime was taken with power supplies E'
and E'' switched off (i.e covering photon energies of 154-792
MeV). We plan to continue with this setting in March and April
2002.
Switch OFF HVs for beam tuning, etc:
To temporarily switch off the tagger High Voltages apply a 50ohm
terminator to the control line at the patch pannel in the A2
messraum.