R&D Plan on Light Collection Takeyasu Ito Los Alamos National Laboratory

2 Light Guides and PMT’s LHe N euv TPB coating  tpb :Solid angle subtended by the TPB coating at the location of the 3 He+n reaction  conv : conversion efficiency A trap : trapping efficiency  trans : transport efficiency  pmt : quantum efficiency PMT One or more thermal break(s) Schematic of light collection / detection Requirements—20 p.e. per event (for particle ID)

3 Number of Photoelectrons N pe : number of photoelectrons N euv : number of extreme ultraviolet photons – N euv = E deposit f prompt / e euv – E deposit = 760keV; e euv = 16 eV – f prompt = 35% for , 9% for  when E=0 kV/cm p, t should be somewhere in between – Using f prompt =9% gives N euv = 4.3x10 3 euv photons  tpb : solid angle subtended by the TPB coating at the location of the n+ 3 He capture event  conv : conversion efficiency of TPB (~0.3 for TPB in plastic matrix) A trap : fraction of the visible photons that meet the condition for the transmission by total internal reflection in the light guide (~0.17 )  trans : efficiency of the light transport in the light guide  pmt : quantum efficiency of the photocathode of the PMT (~0.15 )

4 Extracting light from both edges of the side walls Need  trans > 60% Operate PMTs at 4K to reduce loss due to thermal breaks (R&D underway) A Possible Geometry

5 Questions that need to be answered by the R&D 1. Can we get N euv > 20 (or  trans > 60%) in the geometry that can be used in the EDM experiment? 2. How does the EUV scintillation light yield (for both prompt and afterpulse) change with the electric field? 3. What is f prompt for p and t from neutron capture on 3 He?

6 Test #1 Purpose: – Measure (geometry dependent factors)  Note: – Map the position dependence Method: – Build a full scale mock-up/prototype of the measurement cell + light guide system – Fill the cell with Ar gas and use the 128nm scintillation light caused in the Ar gas by  particles – Measure the number of p.e.’s and compare it to that obtained from a more simple known geometry (control experiment)

7 Test #1 schematic ~1.2 m ~0.6 m 2” tubes (upto12) Ar gas Light tight, gas tight box  source(s) Measurement cell Light guide

8 A few remarks on Test #1 The energy deposition necessary to create one 128 nm photon in Ar is 67.9 eV. – In principle, we know N euv for  in Ar, but not  conv. Therefore we need the control experiment, which determines N euv  conv.  ’s mean range is 3-4cm in 1atm Ar gas (for 241 Am). – Need MC to calculate  tpb to interpret the control experiment. The photon yield is very sensitive to the contamination in Ar gas.

9 Test #2 Purpose: see if the liquid helium scintillation light yield (both prompt and afterpulse) changes with the electric field Method: – Stick light guide between the electrodes in the HV test apparatus – The front face of the light guide is coated with TPB – Place  (and  source(s) in front of the front face of the light guide – Measure the light yield as a function of the applied electric field – By keeping the electrode separation small (up to ~2cm), it is possible to generate a high electric field.

10 Test #2 schematic  or  source TPB coated surface PMT LHe K Light guide (Acrylic rod with rounded off edge) existing10” port

11 Test #2 schematic PMT housed in vacuum

12 Budget ItemTestBudget($)Note Aluminum dark box#15,000 PMTs (x10)#16,000$600 each, we already have 2, need 12 Gas handling system#1500Flowmeter, bubbler Measurement cell#11,000 Light guides#15,000 Engineer’s time (40hrs)#15,000 Technician’s time (80hrs)#110,000 Light guide#2500 Low temp PMT#20We own 3 Low temp PMT base#2300 New flanges#22,000 Engineer’s time (20hrs)#22,500 Technician’s time (80hrs)#210,000 Liquid helium (500 liter x 3)#24,500 DAQ computer#1&21,500 VME crate + modules#1&215,000Crate, ADC, Waveform digitizer Radioactive sources#1&23,000 total71,800

13 Test #1 Schedule ActivityDurationBeginEnd Preliminary design2 months10/15/200612/14/2006 Final design2 months12/15/200702/14/2006 Procure PMTs3 months12/15/200603/14/2006 Procure radioactive source3 months12/15/200603/14/2006 Procure DAQ system3 months12/15/200603/14/2006 Procure measurement cell2 months02/15/200704/14/2007 Procure light guide3 months02/15/200705/14/2007 Procure gas system parts2 months02/15/200704/14/2007 Procure dark box2 months02/15/200704/14/2007 Setup DAQ system1 month03/15/200704/14/2007 Assemble apparatus1 month05/15/200706/14/2007 Perform measurements2 month06/15/200708/14/2007

14 Test #2 Schedule ActivityDurationBeginEnd Preliminary design2 months10/15/200612/14/2006 Final design2 months12/15/200602/14/2006 Procure radioactive sources3 months12/15/200603/14/2006 Procure DAQ system3 months12/15/200603/14/2006 Procure light guide1 month02/15/200703/14/2007 Procure new flange, view port, PMT housing2 months02/15/200704/14/2007 Procure PMT base2 months02/15/200704/14/2007 Setup DAQ system1 month03/15/200704/14/2007 Assemble apparatus1 month Perform measurements1 month