Development of cryogenic silicon detectors for the TOTEM Roman pots

Transcription

1 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

2 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 Seminar on Solid State Detectors 2

3 Integration of the TOTEM Roman pots in LHC 94 m, 154 m and 180 m from IP Seminar on Solid State Detectors 3

4 Layout of a Roman pot station Seminar on Solid State Detectors 4

5 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 Seminar on Solid State Detectors 5

6 Edge current vs. bias potential and temperature - Preliminary results Sensor 1, T = 150 K Sensor 2, T = 130 K Current (na) Current (µa) U = 500 V a) 10-1 Sensor 1 Sensor 2 b) Reverse bias potential (V) Temperature (K) Seminar on Solid State Detectors 6

7 Module design Pitch Adapter APV25 Hybrid Support Detector Spacer Cooling Pipe Seminar on Solid State Detectors 7

8 Summary of heat loads Seminar on Solid State Detectors 8

9 Temperature ranges for cryogenics and refrigeration Seminar on Solid State Detectors 9

10 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 Seminar on Solid State Detectors 10

11 Working fluids for evaporative cooling at 120 K Seminar on Solid State Detectors 11

12 Cooling Methods Joule-Thomson Process 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 K T is 381 K K / 6.7 bar ihx η is = 0.7 x = 0.1 x = K w t q enthalpie h [kj/kg] Seminar on Solid State Detectors 12

13 Cooling Methods Flooded System pressure p [kpa] log p, h-diagram for Argon Data Source: GASPAK, Version 3.30 (Cryodata Inc.) 1000 (w t ) q K / 6.7 bar x = 0.5 q C = q enthalpie h [kj/kg] Seminar on Solid State Detectors 13

14 Principle of cooling Seminar on Solid State Detectors 14

15 Heat Sink Gifford-McMahon Cryocooler Integral Stirling Seminar on Solid State Detectors 15

16 Thermal interface condenser / receiver Seminar on Solid State Detectors 16

17 Cryogenic Micro Pump Seminar on Solid State Detectors 17

18 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 = ) u no correlation u few data for single-phase flow published Seminar on Solid State Detectors 18

19 Calculated pressure drop in the Roman pot detector modules Local Pressure Gradient (bar/m) Saturation Temperature: 120 K Cooling Capacity: 3 W Tube Diameter: 0.3 mm Mass Flow Rates: Methane g/s Argon g/s Integrated Pressure Drop (bar) Methane (G = 172 kg/m²s) Argon (G = 606 kg/m²s) x in = 0 ; x out = Quality (-) Tube Length (m) Seminar on Solid State Detectors 19

20 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 Seminar on Solid State Detectors 20

21 Peng s nucleation criterion for microtubes N mb with N mb = c π 1 h lv a v ( v v ) q& D h Heat Flux (W/m 2 ) K 120 K 120 K Diameter (mm) Seminar on Solid State Detectors 21

22 Calculated HTC in the Roman pot detector modules 50 Local Heat Transfer Coefficient (kw/m 2 K) Saturation Temperature: 120 K Cooling Capacity: 3 W Tube Diameter: 0.3 mm Mass Flow Rates: Argon g/s Methane g/s Convective Boiling Quality (-) Nucleate Boiling Argon (G = 606 kg/m²s) Methane (G = 172 kg/m²s) Seminar on Solid State Detectors 22

23 Test circuit layout Seminar on Solid State Detectors 23

24 Test Stand - Total View Seminar on Solid State Detectors 24

25 Test Stand - Cooling Rack Seminar on Solid State Detectors 25

26 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 Seminar on Solid State Detectors 26