“MUON” Collaboration meeting Tracking system PNPI Status report A.Krivshich June 14, 2004 “MUON” Collaboration meeting Gatchina, Russia

for μp-capture experiment Tracking system for μp-capture experiment E РС 1 РС 2 ТРС μ - muons

Proportional chambers and PC-2 Two sets of PC2 electrodes under production. It order to finish the PC2 production and start its testing we would propose to discuss and fix a possible amount of materials in the PC2 cathodes during this workshop. New design of cathode. Aluminum. Thickness 40m. Soft. Aluminum. Thickness 40 m. Hard. Aluminum. Thickness 10m. Soft. Aluminized Mylar (50m). Old design of cathode. Diameter of wires 55m. Stainless steel. Wire spacing is 1 mm.

Time Projection Chamber TPC#1. It is tested about 15 months. TPC#2. It is tested about 3 months. TPC#3. It has to be assembled after finishing of TPC#1 and TPC#2 tests.

TPC production chain Frame manufacturing at PNPI Print circuit depositing at STU Electrode wiring at PNPI Ultra sound cleaning Dust control by light emission in nitrogen TPC assembling in clean room TPC testing in vessel Nitrogen Hydrogen Gas supply system

ТРС № 1 Date of TPC birth – 18 February 2003 90Sr Old (PNPI) vessel Date of TPC birth – 18 February 2003 Туре of vessel - Old one (PNPI) Gas admixtures Oxygen Nitrogen Water After filling ≤0.5 ppm ≤0.5 ppm ≤1 ppm One month after filling ≤1 ppm 8 ppm ≤ 1 ppm

Testing results- Idc ≤ 2nA (HV = 6500V) TPC#1. Stage # 1 Gas - Nitrogen Pressure - 5 Bar Training period - 7 days Training results - Idc ≤ 2nA (HV = 7000V) Testing period - 11 months Heating conditions - 1200C; 24 hours; 4 times. Tests duration - 5 months. Testing results- Idc ≤ 2nA (HV = 6500V)

Test results - Idc ≤ 5nA (HV = 6500V) Pressure - 10 Bar Testing period - 10 days TPC#1. Stage # 2 Date of start – 4 February 2004 Gas - Hydrogen Test results - Idc ≤ 5nA (HV = 6500V) Outer cathode wire has been broken in the solder point. Chamber was disassembled. The wire was taken out. Chamber was assembled again.

Results of the TPC#1 electrodes Dark current after chamber assembling visual inspection No traces of dust. No dark spots on the anode. A few light-gray spots (2-3mm diameter) have been observed on the cathode planes. Dark current after chamber assembling Idc ≤ 5nA (HV = 6500V)

Periodic breakdowns occurred Breakdown current exceeded 50A under HV=6500V. Time interval between the breakdowns under irradiation by 90Sr source 67 hours …………………. HV=5300V 48 hours …………………. HV=5400V 48 hours …………………. HV=5500V 6 hours …………………. HV=5600V Long term operation characteristics of TPC#1 under irradiation At HV = 5200V (I = 2nA) No breakdowns during one month

Conclusion about TPC#1. 1. The results obtained during more than one year of TPC#1 operation looks quite well. We believe that TPC design and technology of its assembling are reliable and quite promising. 2. A couple of days ago TPC#1 has been taken out from the vessel to study the reasons of breakdowns. 3. The main possible reason of the breakdown occurring is the charge accumulation on the dielectric with consequent discharge. 4. Very probable that main reason of breakdowns is some mistake during TPC assembling.

ТРС #2 90Sr Date of TPC birth – 24 March 2004 Туре of vessel - New one (PNPI+PSI) Stage #1 Gas - Nitrogen Pressure - 5 Bar Training period - 3 days Training results - Dark current is rising up/down from 0.005 to 6A at HV=5200V. It was fixed the number of anode wire which are associated with this current. Conclusion: take out TPC from the vessel to see what happened.

Results of the TPC#2 electrodes visual inspection 1.No traces of dust. 2.No dark spots on the anode. 3.One dark spot (3mm diameter) has been observed on the cathode (top) directly in front of labeled anode wire . Date of start – 6 April 2004 (One week later) Gas - Nitrogen, 5 Bar Test duration - One week Stage #2 HV=5400V HV=6300V Neighbor wire 0.6 A 2.4 A Central wire 2.5 A 3.0 A Neighbor wire 2.2 A 3.0 A

Currant from central wire Total currant Currant from central wire Nitrogen. 5 Bar.

Stage #3 Conclusion: take out TPC from the vessel to see Gas - Hydrogen. 10 Bar Date of start – 14 April 2004 Testing period - 7 days Obtained results. 1. TPC is running more unstable. First trip (10A) was at HV=4700V. 2. Current in hydrogen exceeds current in nitrogen by 2-3 times. 3. Dark current is about 20A at HV=6200V. Conclusion: take out TPC from the vessel to see what happened again.

Results of the TPC#2 electrodes visual inspection 1.No traces of dust. 2.No dark spots on the anode. 3.Three dark spots have been observed on the cathodes. 3.1. Two of them are placed symmetrically with respect each other directly in front of labeled anode wires. 3.2. Diameter of top (cathode) spot increased up to about 12mm. 3.3. Diameter of bottom (strip-cathode) spot was about 7mm. 3.4. Third spot had diameter about 3mm and placed far away from mentioned above sports.

Element distribution along the hot spot that are placed on the cathode wires Strip-cathode Cathode

90Sr source has been collimated Actions 1. Cathode wires with spots have been replaced by new one. 2. TPC was assembled again. 3. Hydrogen. 10 Bar. 4. Date of start – 4 June 2004 5.Testing period - 1.5 months (till now) 6. Main cathode - HV = 25 kV Stage #4 90Sr 90Sr source has been collimated

After taking out of cathode wires with two hot spots the dark current behavior improved significantly. So, the point where dark current is rising up more than 100 times has been shifted from HV=4.7kV to about 5.8kV.

Summary We feel ourselves quite optimistic because the life become more better. At the moment we have quite good experimental facilities to perform the TPC study at PNPI. We can work with two TPC simultaneously and we do it. 2. Working characteristics of TPC#1 and TPC#2 looks quite promising. Our goal is to investigate TPC behavior, including extremely high working conditions. TPC must be reliable working device. 3. It is necessary to investigate the nature of dark spots on the cathodes and prevent their creation. 4. We are going to start production of TPC#3 and TPC#4 only after finishing of TPC#1 and TPC#2 investigations. 5. We believe that at least one of these TPC will work in the next our beam run at PSI.