1. High Voltage MUX for ATLAS Tracker Upgrade EG Villani STFC RAL on behalf of the ATLAS HVMUX group TWEPP-14, 22 – 26 Sept. 2014

2. HV MUX motivation and principle HV MUX devices requirements Real time test system and test results Conclusions Outline

3. 1 ATLAS Phase II Tracker Upgrade Challenges facing HL-LHC silicon detector upgrades Higher Occupancies (  200 interactions / bunch crossing) ⤷ Finer Segmentation Higher Particle Fluences (  10 14 outmost layers to  10 16 innermost layers ⤷ Increased Radiation Tolerance (  10 increase in dose w.r.t. ATLAS ) Larger Area (~200 m 2 ) ⤷ Cheaper Sensors More Channels ⤷ Efficient power/bias distribution / low material budget Phase 2 (HL-LHC) Replacement of the present Transition Radiation Tracker (TRT) and Silicon Tracker (SCT) with an all-silicon strip tracker Conceptual Tracker Layout Short Strip (2.4 cm)  -strips (stereo layers): Long Strip (4.8 cm)  -strips (stereo layers): r = 38, 50, 62 cm r = 74, 100 cm From 1E33 cm -2 s -1 …to 5E34 cm -2 s -1 TWEPP-14 25/09/2014

4. HV distribution in ATLAS Upgrade The ‘ideal’ solution would be one HV bias line for each sensor: High Redundancy; Individual enabling or disabling of sensors and current monitoring; But the increased number of sensors in the Upgraded Tracker implies a trade off among material budget, complexity of power distribution and number of HV bias lines. Use single (or more) HV line to power all sensors in a ½ stave and use one HV switch under DCS control for each sensor to disable malfunctioning detectors. 2 HV SW TWEPP-14 25/09/2014

5. The Stave concept and HV distribution in ATLAS Upgrade 3 ~ 1.2 meters Bus cable Hybrids Coolant tube structure Carbon honeycomb or foam Carbon fiber facing Stave Cross-section A Stave250 Designed to reduce radiation length  Minimize material by shortening cooling path  13x2 Modules glued directly to a stave core with embedded pipes Designed for mass production  Simplified build procedure  Minimize specialist components  Minimize cost TWEPP-14 25/09/2014

6. 4 HV distribution in ATLAS Upgrade TWEPP-14 25/09/2014

7. HV devices requirements 5 High Voltage switches strip detector requirements: Must be rated to 500V plus a safety margin; Must be radiation hard, nominal maximum expected  1x10 15 n eq /cm 2,  30Mrad (Si) for end cap. Multiply by (up to) 2 to include safety margin; On-state impedance R on << 1kΩ // I on  10mA (for irradiated sensors) Off-state impedance R off >> 1GΩ // I lkg << I sens Must be unaffected by magnetic field; Must maintain satisfactory performance at -30  C; Must be small (area constraint) and cheap (around 1E4 needed) TWEPP-14 25/09/2014

8. HV devices investigated HV Si, SiC and GaN based devices are being investigated 6 FAILED PASS – need conf. T.B.T. FAILED PASS – N.A. FAILED TWEPP-14 25/09/2014

9. Background PCB JFETsI ds I gs I ds VgVg VgVg VgVg Pre irradiation JFET3 JFET4 Si JFET 2N6449 V ds =285V V ds =150V PCB JFETs I ds IgIg IgIg V gs JFET3 V gs JFET4 Post irradiation 7 TWEPP-14 25/09/2014

10. Real Time HV devices radiation tests 8 Real time HV devices test system: it allows monitoring devices’ behaviour when irradiated Real time Monitoring of r ds and I ds vs. V gs vs. particle fluence Data are saved at 1 sample/sec for offline analysis Two devices simultaneously, it can be used for generic real-time testing of devices under radiation IEEE488/USB 2602 ½ HV Vds and Ids tot Vgs and Igs Is 2602 ½ Is  15 m Source meters Q1Q2 HV 2410 2602 ½ PC - Labview Particle Beam TWEPP-14 25/09/2014

11. HV mounting frame 9 Plexiglas Frame with X-Y adjustments to mount DUT HV devices. PCB to hold up to 4 HV devices PCB in the cool box cool box TWEPP-14 25/09/2014

12. HV mounting frame 10 Beam alignment checked with photo film on area where DUTs are placed cool box Level of radiation near the cool box after an irradiation test. TWEPP-14 25/09/2014

13. HV devices radiation tests 11 A number of HV devices tested at Birmingham last weeks, including: EPC2012 (GaN FET) CPMF-1200 (SiC MOSFET) 2N6449 (Si JFET) EPC2012 CPMF-1200 2N6449 EPC2012 TWEPP-14 25/09/2014

14. Irradiation test synopsis 12 EPC2012 EPC2012: r ds @ constant mA’s test; V ds test at 150 V, 1mA compliance, V gs =[-1, 3]V/20mV time RAD Annealing + Ids plots: 5 mins Rds measurement: 1 min EPC2012: 20 irradiation phases, 0.5 minute/ each @ Beam current 0.2 μA = 1.25e12 p + /sec. Rest phases in between irradiation phases around 5 minutes I ds bias current increasingly higher, to emulate sensors leakage with dose 4 4 6 6 8 8 10 Rds measurement mA TWEPP-14 25/09/2014

15. time 13 RAD * At Beam current 0.2 μA = 1.25e12 p + /sec. * For 26MeV p + 2e15 1MeV n-eqv in ≈ 533 seconds (in Si – no data for GaN) * 20 irradiation phases of 30 seconds/each = 2.25e15 1MeV n- eqv (estimated MAX fluence for Strips is 2e15 1MeV n-eqv, including x2 safety factor) * Max ΔT ≈4.5°C/sec HV devices radiation tests beam sequence Annealing + Ids plots: 5 mins Rds measurement: 1 min TWEPP-14 25/09/2014

16. Constant I ds for r ds measurement 14 EPC devices radiation tests results Irradiation phases V gs sweep DUT1/2 alternately ON TWEPP-14 25/09/2014

17. 15 EPC devices radiation tests results V gs sweep Irradiation phases I s1, I s1 Magnified Time plots of board B DUTs I s1/2 during the radiation test. TWEPP-14 25/09/2014 V ds

18. 16 EPC devices radiation tests results Irradiation phases 30 sec/each V gs sweep Irradiation phases (30 + 30 sec.) Time plots of board B DUT 1 I g during the radiation test. TWEPP-14 25/09/2014

19. EPC devices radiation tests results Average I g and 1 σ @V gs =3V (device fully on). Average and 1 σ deviation I s and I g Leakage current @V ds =150V, V gs =0V. 17 V ds =150V V gs =3V TWEPP-14 25/09/2014 Average r dson < 2Ohm @V gs =3V

20. We could use HV devices rated for lower voltage than needed and stack them on each other to achieve higher voltage switching the biasing circuit needs careful designing, to avoid overvoltages and / or excessive leakage Modeled circuit with parasitic resistor values taken from measurements of our own EPC devices. 18 Stacked configuration for high voltages Not part of circuit; just mimics actual measured leakage currents Also not part of circuit TWEPP-14 25/09/2014

21. 19 Stacked configuration for high voltages TWEPP-14 25/09/2014 V load simulated V load measured

22. 20 Stacked configuration for high voltages First Pass Estimating Size of EPC2012 Circuit Used only commercial components Did not do real layout Size is large but optimization possible TWEPP-14 25/09/2014

23. Conclusions High Voltage distribution via HV switches and DCS control is being investigated. A test system has been developed to allow real time monitoring of the DUTs during irradiation. A number of devices, based upon Si and wider band gap materials, are being investigated. GaN seems promising, will need to be confirmed. The control circuitry to enable and disable the HV switches also being investigated. Thank you! 21 TWEPP-14 25/09/2014

24. I Backup - HV devices example plots – EPC2012 EPC2012 I ds vs. V gs, V ds max = 200V, I ds compliance= 1mA EPC2012 I gs vs. V gs, V ds max = 200V V gs (V) I ds (A) I gs (A) V gs (V) DUT#1, Board A GaN devices rated for up to 200V ( up to 600V would be needed for HV MUX but stacked configuration possible – see later slides) TWEPP-14 25/09/2014

25. Backup - HV MUX control scheme Negative HV multiplier filter HV JFET DEPL V source Regardless of the devices used as HV switches, a control circuitry, referenced to a high potential, to enable them is needed An investigated option consists of an AC coupled control switch based upon a voltage multiplier (it works with depletion and enhancement mode devices depending on the polarity of the diodes ) -HV To Detector II TWEPP-14 25/09/2014

26. * The voltage across R2 is measured vs. amplitude and frequency of V in ( square wave, 50% duty cycle) and for V high = [0, -300] V * Applying -300 V a slight decrease in abs(V out ) is noticed (some leakage current over the board surface is the likely cause) ‘DABO’ connection Voltage MPY ‘MOBO’ f in = 50 kHz V bias =0V f in = 100 kHz V bias =0V f in = 50 kHz V bias =-300V V MPYV out V in Multimeter : Fluke 287 Signal generator: Tektronix AFG3252 HV PSU: EA-BS315-04B (#2 in series to get 300V) (HV PSU) (Sign. Gen) (Meter) III Backup - HV MUX control scheme test TWEPP-14 25/09/2014