CHIPS Run Feb-2008
2-25-08
Configure 25 Mev Beam line
NaI Detector
PMT HV 1500 Co-60 1microCi source: 1MeV band at about 55mV
PMT HV 1500 no source, noisey tube
IAC NaI Detector Calibrated with Co60 source with high voltage power supply at 1500 Volt
Beam Profile
1.5 inch FWHM beam profile measured at 8 mA peak current. The units on the beam scan is in inches. so the grid is 2inch by 2 inch (5cm by 5cm). Frequency is 60 Hz.
_________________________________ 4 mA peak current
_______________________________________________
Beam on
15:20:
Turned beam on zero degree port and NaI lights up whan positioned just after the beam pipe window.
Must be gammas Rate = 10 count/sec. Anode amplified (x64) then discriminated and put into a scaler. Threshold on discriminator is 2 Volts and results in zero counts when beam off. NaI PMT at 1500 volts.
15:30:
Now move NaI detector so it is near experimental Cell wall. Just inside the wall
Gamma rate goes to zero!
Now change scope to 5 sec accumulation. 1 Mev electron should give 55 mV pulse on scope.
16:00:
Now try to put electrons into Experimental cell.
We turned on the first dipole to deflect 10 MeV electrons onto the Tungsten target. The quads between the two dipoles were used to minimize the rates on the NaI. Then we turned on the last dipole to deflect 3 MeV electrons into the Experimental cell. And measured the following rates
811 counts /15 sec threshold at a minimim
Now insert 1.2 cm thick Aluminum plate in front of the NaI in order to capture all the electrons and measure the gamma rate.
776 counts /15 sec threshold at a minimim
2-27-08
Channel 6 : IAC NaI : Co-60 source gave 20 mV pulses on scope when PMT at 1200 Volts
Channel 10: JLab NaI : Co-60 source gave ~40 mV pulses on scope when PMT at 1400 Volts
Positron Runs with DAQ
Run 393: 1400 V JLAB NaI, 1209 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) OR (Gun AND NaI2), 50 mV Discriminator Threshold
Run 394: 1400 V JLAB NaI, 1209 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 50 mV Discriminator Threshold
Run 395: 1400 V JLAB NaI, 1209 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold
Run 396: 1400 V JLAB NaI, 1209 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold, Increase dynode amplier from x20 to x50 to raise trigger threshold.
Run 397: 1500 V JLAB NaI, 1300 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold, Increase dynode amplier at x50 to raise trigger threshold.
Run 398: 1500 V JLAB NaI, 1300 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold, Increase dynode amplier from at x50 to raise trigger threshold. Insert 4" thick Aluminum in front of positron stop. SHould see rate die if we have positrons but gammas will come through.
Start time:16:03:25 Stop Time: 16:23:57
47 Count/60 seconds
Run 399: 1500 V JLAB NaI, 1300 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold, Increase dynode amplier from at x50 to raise trigger threshold. Removed 4" thick Aluminum in front of positron stop.
252 counts/ 60 seconds
Changed first dipole and measured 10 mA beam current after zero degree port
Run 400: 1500 V JLAB NaI, 1300 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold, Increase dynode amplier from at x50 to raise trigger threshold. Change last dipole polarity. Check electron rate .
172 counts/min
Run 401: 1500 V JLAB NaI, 1300 Volts on ISU NaI, Trigger: (Gun AND NaI 1 ) AND (Gun AND NaI2), 30 mV Discriminator Threshold, Increase dynode amplier from at x50 to raise trigger threshold. Change back to Positron polarity. Check electron rate
.
242 counts/min
Histograms
The histograms below are the results of previous runs. Brick means, all the positrons were stopped at the brick and coincidence measruement was made to detect secondaries, background and noise. NOBrick means, the Al brick was removed and only 2"X2" Al absorber exist. The bottom histograms are the subtractions of brick and NOBrick histos for each NaI.
