Tracking system PNPI Status report A.Krivshich June 14, 2004 “MUON” Collaboration meeting Gatchina, Russia
РС 1 E ТРС μ - muons РС 2 Tracking system for μp-capture experiment
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 40m. Soft. • Aluminum. Thickness 40 m. Hard. • Aluminum. Thickness 10m. Soft. • Aluminized Mylar (50m). Old design of cathode. Diameter of wires 55m. 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.
Electrode wiring at PNPI Frame manufacturing at PNPI Ultra sound cleaning Dust control by light emission in nitrogen TPC assembling in clean room Print circuit depositing at STU Hydrogen Nitrogen Gas supply system TPC production chain TPC testing in vessel
90Sr Old (PNPI) vessel ТРС № 1 Date of TPC birth – 18 February 2003 Туре of vessel - Old one (PNPI) Gas admixtures Oxygen NitrogenWater After filling≤0.5 ppm ≤0.5 ppm≤1 ppm One month after filling ≤1 ppm 8 ppm≤ 1 ppm
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)
Outer cathode wire has been broken in the solder point. Chamber was disassembled. The wire was taken out. Chamber was assembled again. 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)
Results of the TPC#1 electrodes 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 50A 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.
90Sr ТРС #2 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 6A 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=5400VHV=6300V Neighbor wire0.6 A2.4 A Central wire2.5 A3.0 A Neighbor wire2.2 A3.0 A
Nitrogen. 5 Bar. Total currant Currant from central wire
Stage #3 Gas - Hydrogen. 10 Bar Date of start – 14 April 2004 Testing period- 7 days Obtained results. 1. TPC is running more unstable. First trip (10A)was at HV=4700V. 2. Current in hydrogen exceeds current in nitrogen by 2-3 times. 3. Dark current is about 20A 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 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 – 4June 2004 5.Testing period- 1.5 months (till now) 6. Main cathode - HV = 25 kV Stage #4
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.