On Detector electronics: PMT HV system

1. On Detector electronics: PMT HV system Tile Upgrade Workshop (CERN- February 2008 8 and 9) François Vazeille • Reminder about the Tilecal set-up Design, production and tests (Clermont-Ferrand)  Specifications and performances • Reminder about safety factors on radiation effects • Possible improvements

2. Reminder about the Tilecal set-up … and about the individual regulation loop • Tilecal in-situ regulation • Based on one Optocoupler chip/channel • Use of an external HV (common to 24 Channels) located in USA15 room HV out Opto coupler From DAC • Loop working stand-alone once the DAC value is set by the user via the DCS (…even though the DCS is lost or if the HV Micro is dead) From HV Source

3. … and about the general set-up in the pit  2 main elements: - HV Source (USA15) - HV Distributors (UX15) USA15 HV PC LVCAN PC + Associated elements and connections: - CANbus and LVCAN PS (and LVCAN PC) - DCS: HV PC + CAN interfaces - fLVPS HV Source LVCAN Patch P Internal HV Bus Flex Bus External HV bus Long cable Internal HV Opto External HV Opto HV Micro fLVPS Short cable HV Distributors of Super-Drawer (6 cards/Super-Drawer) Daisy chain Comment: LVCAN Power Supplies separated for HV and the Integrator ADC It is an advantage for me because the 2 systems are very different.

4. HV Distributors • 5 types of cards - Bus cards: Stiff Internal, Stiff External, Flexible • - Opto cards (Optocouplers) • - Micro cards (Microcontrollers) • The Microcontroller (MC68376) plays 2 roles: - Control of the Opto and Micro cards - CANbus Interface (with a LV regulator powered by a CANbus PS) Bus cards: 270 Stiff Internal 270 Flexible 270 Stiff External 90x1310 mm2

5. 110x600 mm2 100x170 mm2 540 Opto cards + other spares 270 Micro cards + other spares + Making and use of dedicated Test Benches for each type of cards, several times used before, during and after burn-in + Drawers Test Benches +In particular: Very Long Term Test of Opto cards (Full Daisy chain) associating HV Distributors and HV Source Specifications and performances • Specifications: (HV) < 0.5 V in order to have G/G < 0.5% on PMTs • Performances: (HV) < 0.1V from Clermont-Fd, Test Beam and Pit results Comment: some induced noise on the readout. Proper to any HV system and due to the whole front-end scheme but that does not mean that improvements could not be made in the future.

6. Reminder about safety factors on radiation effects  Studies (Tilecal notes) made about: - TID and NIEL doses on cmos and bipolar components - SEE TID: Total Ionizing Dose NIEL: Non Ionizing Energy Loss SEE: Single Event Effect • ATLAS rules on safety factors

7. We will consider 3 steps: - Nominal Luminosity: 1034 - Ultimate Luminosity: 2.3 1034 - Ultimate SLHC: 10 1034 Tables of safety factors as requested and as measured (worst location), for 5 years running in each scenario  TID • - For the HV Opto: it affects generally 1 channel only. • - New tests for bipolar could be requested if the required safety stays at 70, • because of the large uncertainty on simulations (Factor 3.5) • The first ATLAS radiation results will bring useful information.

8.  NIEL Quoted in parenthesis: pre-prod components - For the HV Opto: it affects generally 1 channel only. - New tests could be requested if the required safety stays at 50, because of the large uncertainty on simulations (Factor 5)  The first ATLAS radiation results will bring useful information.  SEE from tests equivalent to 10 years at 1034 - Latch-up effect: on one Micro card inducing Zero voltage/week  Recovered by a power cycle of the Tilecal affected component (here the Super-Drawer) once per day (as foreseen for the whole Tilecal) Comment: 3 SEU per minute in the whole Tilecal - No destructive SEU during the tests: What would be the results at a higher luminosity?  The first ATLAS results will bring useful information, in particular about the large simulation factor (5). Conclusion: no so far about radiation effects  First ATLAS results waited.

9. Possible improvements … always possible once the experience comes at the full scale from the whole detector …  Why an in-situ regulation? • To optimize both the regulation close to the channels and the noise effects • (no pick up on very long cables) • + separation of HV side and readout-side. - To save money: no equivalent commercial product.  Possible improvements from the most important to others • The most important: direct link with fLVPS (mainly a hardware link), • in particular in case of a destructive SEU. - New HVFLEX (already found … but expensive). - Noise killers integrated in the cards on every channel (HVBus or HVOpto). • Better optimized design of the HV tracks on the HVBus boards • (Possible source of noise). - Individual switches (And not 1 for 12 channels) … but more expensive.

10. BUT some components would become obsolete if too many things were changed! • Why not taking benefit of Micro-electronics? • Why not using rad-hard components? But cost!  Are there alternative solutions? - Everything in the counting room? • Come back to the starting point: - Space in USA (Take as reference the volume of Prague HV Source) - 10 000 long cables - Noise problems - Cost if commercial unless moving the present HV Distributors in USA15 ? … - Everything in the cavern but outside the Modules?  The worst solutions: radiations higher than in the Girders.

11. First conclusions • We need to know better the whole HV system, including the HV Source and the fLVPS + the CANbus PS in order to finalize the specifications of what could be a perfect system. • So we must execute the HV Commissioning as foreseen in the WP10 possibly by revising it (My job in the next weeks). • We are not very far from what would be needed at the radiation level and the ATLAS running will provide very useful information on: • - The true radiation levels  Safety factors revised. • - The behavior of the HV system.  New radiation tests will be likely requested. • It is not clear that an upgrade should be needed, even though some weak points would stay.  A medium solution could be a smooth upgrade: the most important points, without remaking everything, saving time and money.