09-08-2016

Study forward detector gamma flash

with Pb curtains

Run #	D90 n Rate (Counts/pulse)	Configuration
5302		11.1 MeV , 2 ns pulse width , 450 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is DU , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Installed 3rd collimator wall, D30 has one 1/16" thick lead curtain
5303		11.1 MeV , 2 ns pulse width , 450 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is DU , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Installed 3rd collimator wall, D30 has NO lead curtain

Shielding & Beam dump impact on gamma flash

Run #	D90 n Rate (Counts/pulse)	Configuration
5300		11.1 MeV , 2 ns pulse width , 450 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is Empty , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,
5301		11.1 MeV , 2 ns pulse width , 450 mA , 200 Hz , Accelerator side collimator open to '0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is Empty , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand, Installed 3rd collimator wall, removed line of site between D30 and cell wall collimator
5305		11.1 MeV , 2 ns pulse width , 300 mA , 90 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain,
5306		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain,
5307		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain,
5308		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is ~0.5 mm x 7 cm x 4 mm Thorium , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain,
5312		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, Install 16" deep x24" wide x 14" high ALuminium photon beam dump. Beam upstream side of dump is 37" from wall
5313		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace aluminium dump with a half lead brick centered on 2" wide beam left right
5314		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace aluminium dump with a half lead brick centered 4" from beam center
5315		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace aluminium dump with a half lead brick centered 2" from beam center |-
5316		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right

Tuning impact on gamma flash

We set up a veto to create a signal that represented the second peak of the gamma flash in D270 & others. A veto pulse was created for the LED to prevent it from outputing a logic high during the first 20 ns after the beam pulse.

Run #	D90 n Rate (Counts/pulse)	Configuration
5309		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, Veto OUT40px
5310		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, Veto IN40px

Thorium plate rates.

Run #	D90 n Rate (Counts/pulse)	Configuration
5316		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5317		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator open to 0.2563 cm, Cell side collimator OPEN to 2 cm , radiator 3/4" IN , Target is Thorium plate orthogonal to beam (90) , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5318		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator wide open to 8 mm slit, Cell side collimator OPEN to 7.5 cm , radiator 3/4" IN , Target is Thorium plate orthogonal to beam (90) , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5319		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator wide open to 8 mm slit, Cell side collimator OPEN to 7.5 cm , radiator 1.5" IN , Target is Thorium plate orthogonal to beam (90) , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5320		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator wide open to 8 mm slit, Cell side collimator OPEN to 7.5 cm , radiator 1.5" IN , Target is EMPTY , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5321		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator wide open to 8 mm slit, Cell side collimator OPEN to 7.5 cm , radiator 1.5" IN , Target is Thorium plate orthogonal to beam (90) , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5322		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator wide open to 8 mm slit, Cell side collimator OPEN to 7.5 cm , radiator 1.5" IN , Target is Empty orthogonal to beam (90) , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right
5323		11.1 MeV , 2 ns pulse width , 300 mA , 200 Hz , Accelerator side collimator wide open to 8 mm slit, Cell side collimator OPEN to 7.5 cm , radiator 1.5" IN , Target is Empty orthogonal to beam (90) , D30 HV changed -1550V, All other detectors at -1700 V, removed pair spectrometer magnet, poly, and stand,Removed 3rd collimator wall, D30 has NO thick lead curtain, replace half lead brick with battle ship steel 17" high 24" deep and 4" beam left right, 1" Al brick on end to have 4" of Al at exit of tunnel of love

End of Run summary

1. The back wall was a source of photons that can be reduced best with blinders
2. The ToF spectrum needs better separation between gamma flash and neutrons, Move detectors back?
3. The tunnel of love reduced the photon singles rate by about 10% for D120 & D150 (compare runs 5300 & 5301).
4. Opening the collimator slit fully caused gamma flash to appear close to the neutron ToF
5. Neutron singles rate in D225 was within the desired rate of 2e-3 n/pulse for a thorium plate target at 90 degrees to the beam
6. D30's rate decreases by a factor of three for every inch of lead shielding added to the front
7. pair spectrometer magnet has little impact on detector background
8. beam tuning may increase photon flash.
9. determine collimator size to produce photon cone that is contained within the photon dump (blinders)
10. cleanup collimator inside wall separating accelerator room and experimental cell

Pictures

Pictures(09-09-2016)

2nCor_44#Run_Plan