Development of cryogenic silicon detectors for the TOTEM Roman pots S. Grohmann, CERN ST-CV RD39 Collaboration Seminar on Solid State Detectors July 11, 2001
Table of contents u u u u Introduction / Roman pots in TOTEM Cryogenic silicon detectors Principle of cooling n cooling methods n working fluids n prototype layout n circuit components n two-phase flow pressure drop and flow boiling n test circuit design Conclusion 11.07.2001 Seminar on Solid State Detectors 2
Integration of the TOTEM Roman pots in LHC 94 m, 154 m and 180 m from IP5 11.07.2001 Seminar on Solid State Detectors 3
Layout of a Roman pot station 11.07.2001 Seminar on Solid State Detectors 4
Cryogenic silicon detectors in the Roman pots Detectors: u x-y strips (10 µm m spatial resolution) u edgeless (min. distance to the beam 20 σ y ) u circular dent u overlapped (relative alignment) u vacuum insulation 11.07.2001 Seminar on Solid State Detectors 5
Edge current vs. bias potential and temperature - Preliminary results - 10 6 10 2 10 5 Sensor 1, T = 150 K Sensor 2, T = 130 K Current (na) 10 4 10 3 10 2 10 1 Current (µa) 10 1 10 0 U = 500 V 10 0 10-1 a) 10-1 Sensor 1 Sensor 2 b) 10-2 10 2 10 3 Reverse bias potential (V) 10-2 100 150 200 250 300 Temperature (K) 11.07.2001 Seminar on Solid State Detectors 6
Module design Pitch Adapter APV25 Hybrid Support Detector Spacer Cooling Pipe 11.07.2001 Seminar on Solid State Detectors 7
Summary of heat loads 11.07.2001 Seminar on Solid State Detectors 8
Temperature ranges for cryogenics and refrigeration 11.07.2001 Seminar on Solid State Detectors 9
Conventional way of sensor cooling at cryogenic temperatures u u sensor directly attached to a cold finger (stirling( or puls-tube) vibrations, space or separation via copper braid small distance, mass fluid circuit with direct evaporation to fulfill requirements in TOTEM 11.07.2001 Seminar on Solid State Detectors 10
Working fluids for evaporative cooling at 120 K 11.07.2001 Seminar on Solid State Detectors 11
Cooling Methods Joule-Thomson Process 10000 pressure p [kpa] log p, h-diagram for Argon Data Source: GASPAK, Version 3.30 (Cryodata Inc.) 120 K / 12.2 bar q C = 1.6 q 0 168 K T is 381 K 1000 110 K / 6.7 bar ihx η is = 0.7 x = 0.1 x = 0.8 300 K w t q 0 100-120 -80-40 0 40 80 120 160 200 240 enthalpie h [kj/kg] 11.07.2001 Seminar on Solid State Detectors 12
Cooling Methods Flooded System 10000 pressure p [kpa] log p, h-diagram for Argon Data Source: GASPAK, Version 3.30 (Cryodata Inc.) 1000 (w t ) q 0 110 K / 6.7 bar x = 0.5 q C = q 0 100-120 -80-40 0 40 80 120 enthalpie h [kj/kg] 11.07.2001 Seminar on Solid State Detectors 13
Principle of cooling 11.07.2001 Seminar on Solid State Detectors 14
Heat Sink Gifford-McMahon Cryocooler Integral Stirling 11.07.2001 Seminar on Solid State Detectors 15
Thermal interface condenser / receiver 11.07.2001 Seminar on Solid State Detectors 16
Cryogenic Micro Pump 11.07.2001 Seminar on Solid State Detectors 17
Two-phase flow pressure drop in microchannels In general: u frictional, accelerational and hydro-static term u correlations for homogeneous and separated flow models (d h 5 mm) u Storek and Brauer: 1 ρ h = x ρ g 1 x + ρ l 1 η correction factor for w v > w l h = x η g 1 x + η l In microchannels: u tube dimensions are in the same order of magnitude as the thermal and hydrodyna- mic boundary layers u Reynolds analogy is no longer valid (Re crit = 200-900) u no correlation u few data for single-phase flow published 11.07.2001 Seminar on Solid State Detectors 18
Calculated pressure drop in the Roman pot detector modules Local Pressure Gradient (bar/m) 15 12 9 6 3 Saturation Temperature: 120 K Cooling Capacity: 3 W Tube Diameter: 0.3 mm Mass Flow Rates: Methane 0.012 g/s Argon 0.043 g/s Integrated Pressure Drop (bar) 0.5 0.4 0.3 0.2 0.1 Methane (G = 172 kg/m²s) Argon (G = 606 kg/m²s) x in = 0 ; x out = 0.5 0 0.0 0.2 0.4 0.6 0.8 1.0 Quality (-) 0.0 0.00 0.02 0.04 0.06 0.08 0.10 Tube Length (m) 11.07.2001 Seminar on Solid State Detectors 19
Flow boiling in microchannels In general: u heat transfer depending on: - operating conditions - fluid properties - heating-wall properties - phase distribution - fluid quality u nucleate boiling: α = f (q) u algorithms only for macroscale tubes with d h 5 mm u Steiner reference quantities: d 0 = 10 mm; m 0 = 100 kg/m²s u u u u In microchannels: simple scaling to our dimensions increases the HTC by factor 10 different flow profiles due to relatively large boundary layers concept of evaporating space and fictitious boiling introduced by Peng few data published 11.07.2001 Seminar on Solid State Detectors 20
Peng s nucleation criterion for microtubes 20000 N mb with N mb = c π 1 h lv a v ( v v ) q& D h Heat Flux (W/m 2 ) 16000 12000 8000 4000 Water @ 373 K Methane @ 120 K Argon @ 120 K 0 0 1 2 3 4 5 Diameter (mm) 11.07.2001 Seminar on Solid State Detectors 21
Calculated HTC in the Roman pot detector modules 50 Local Heat Transfer Coefficient (kw/m 2 K) 40 30 20 10 0 Saturation Temperature: 120 K Cooling Capacity: 3 W Tube Diameter: 0.3 mm Mass Flow Rates: Argon 0.043 g/s Methane 0.012 g/s Convective Boiling 0.0 0.1 0.2 0.3 0.4 0.5 Quality (-) Nucleate Boiling Argon (G = 606 kg/m²s) Methane (G = 172 kg/m²s) 11.07.2001 Seminar on Solid State Detectors 22
Test circuit layout 11.07.2001 Seminar on Solid State Detectors 23
Test Stand - Total View 11.07.2001 Seminar on Solid State Detectors 24
Test Stand - Cooling Rack 11.07.2001 Seminar on Solid State Detectors 25
Conclusion u Edgeless silicon microstrip detectors are being designed for the TOTEM Roman pots with their sensitive area as close as 20 σ y to the beam. u Spatial resolution of 10 µm m is obtained with a pitch of about 50 µm. u A circular dent and the detector overlapping allow relative alignment of the sensors using the measuring data. u Detectors are cooled by direct evaporation in integrated microtubes, which provides minimum mass contribution, constant temperature profiles and extremely high heat transfer rates, and effective decoupling of vibrations. u Experiments are under way to study two-phase flow pressure drop and heat transfer in microchannels and to test the new circuit components. 11.07.2001 Seminar on Solid State Detectors 26