1. SVTRAD Upgrades M. Bruinsma1Sept. 22nd 2003 SVTRAD Upgrades M. Bruinsma bruinsma@slac.stanford.edu September 22, 2003 Background Workshop, SLAC Motivation Diamond sensors Readout electronics upgrade: SVTRAD1.5

2. SVTRAD Upgrades M. Bruinsma2Sept. 22nd 2003 Purpose of SVTRAD 1.Monitor radiation levels and 2.Protect the SVT from excessive and avoidable radiation damage: a)Acute radiation damage: P-stops, blocking capacitor breakdown May occur at acute doses of 1 rad or more Should be detected within ~ 1 ms: “fast aborts” b)Long-term radiation damage: Leakage current increase in Si bulk Noise increase, gain reduction in readout electronics Significant degradation expected after 5Mrad. SVTRAD should keep total dose of SVT modules below 4Mrad Time scale: seconds (monitoring) – minutes (“slow aborts”) – years These are two very distinct protection tasks, both done by SVTRAD.

3. SVTRAD Upgrades M. Bruinsma3Sept. 22nd 2003 Problems with the current system 1.Uncertainty in pedestal (=‘leakage’=‘dark’) current of PIN diode: accuracy ~0.1% => 3nA for 3  A dark current ~ radiation current (15mrad/s) This mainly affects the slow (‘software’) aborts 2.Secondary problems/limitations – SVTRAD board mid-plane diode radiation currents only accurate after long averaging feedback to PEP-II of (mid-plane) radiation levels rather slow (few s) PIN diode is either ‘abort diode’ or ‘monitoring diode’ Abort logic not very flexible Electronic problems (ground fluctuations, etc.) Board-temperature dependencies Upgrade strategy: 1.Replace damaged sensors with CVD diamond sensors in 2005 (=a.s.a.p.) 2.Upgrade readout electronics in end of 2003 (=a.s.a.p)

4. SVTRAD Upgrades M. Bruinsma4Sept. 22nd 2003 CVD diamond sensors From ‘operational’ point of view, diamond sensors are similar to PIN diodes: similar sizes obtainable (10x10x0.5mm) similar current levels due to radiation (100-200pC/mrad) faster response times (ns) higher bias : 500V for pcCVD diamond, 100 V for scCVD diamond (50V for PIN diodes) Diamonds have (virtually) no leakage currents, even after irradiation They are very radiation-hard Have been installed in BaBar and routinely read out with SVTRAD1 board: Proven to be suitable alternative Minor (non-critical) to be understood (current tails, E x B effect) The use of diamond sensors will eliminate the largest systematic uncertainty of the SVTRAD system

5. SVTRAD Upgrades M. Bruinsma5Sept. 22nd 2003 Electronics Upgrade: SVTRAD1.5 Motivation for SVTRAD1.5: Compatible with future diamond sensor operation (500V bias) Enhanced functionality, improved diagnostic power & flexibility in abort decisions Improved precision on temperature- and current-measurement Elimination of electronics problems of current readout board Ensure sufficient spare boards for running until 2010 (no working spares) Note: SVTRAD1.5 will not solve the leakage current problem – diamonds will. (but it may reduce it)

6. SVTRAD Upgrades M. Bruinsma6Sept. 22nd 2003 Conceptual overview of SVTRAD1.5 Diode current front-end (opamps, ADCs) Temp. measurement +switch Abort & monitoring logic (FPGA(s) + EPROM) MCU + CAN & RS232 fibers display (LEDs) PEP HTEMP analog mon. (DACs) JTAG abort monit. I diode V bias scope IOC temp thermistors Diodes/diamonds V therm I therm on-board thermistors SVT p.s.

7. SVTRAD Upgrades M. Bruinsma7Sept. 22nd 2003 Analog outputs for fast monitoring SVTRAD1.5 ‘SVTRAD-DAC’ module: ~1kHz update rate per channel 4 quad DACs with SPI interface AD5544, 16 bit precision NIM module Installed in alcove near PEP-II electronics SVTRAD1.5 optical fibers, 3 per board Digital SPI interface to (quad) DAC (SCLK, CS, DIN) 12 analog diode signals (1kHz) to PEP-II SAM: leakage current subtracted => radiation levels Benefits: Fast feedback to PEP-II operators 1kHz rate can be used to study individual injection pulses

8. SVTRAD Upgrades M. Bruinsma8Sept. 22nd 2003 More flexibility in fast abort decisions All logic integrated into single FPGA: can make an abort decision based on a combination of sensors (MID,TOP,BOT) Abort channel current measurement modified from VFC -> ADC: could include non-linear terms in temperature correction (more precise) could include time-dependence of radiation levels in abort decision, e.g. prevent abort if radiation levels decreasing could prevent abort decision if dose rate over threshold not hazardous for acute damage (i.e. << 1rad/ms) (it then becomes mainly a radiation budget issue) 2ms Dose rate time 0 threshold rate: 1000 mrad/s abort if dose over threshold:~2.5 rad

9. SVTRAD Upgrades M. Bruinsma9Sept. 22nd 2003 Other benefits of front-end upgrade 1.All diodes are both ‘monitoring’ diodes and ‘abort’ diodes 2.Better precision on abort channel (monitoring channel the same) 3.Both ranges completely ‘tunable’: monitoring range extended (7.8  A -> 15  A) for larger leakage currents abort range extended (0.5mA->5mA) (may be lowered for better precision) 4.Faster abort decisions (1ms ->100  s) possible 5.Better (x100) precision on monitoring of ‘abort channel’ (no rerouting) 6.Can store history of abort ADC values: better verification of abort decision good fast-history of abort channel currents Not fully-explored option: Issue fast hardware ‘warning’ signal that would automatically undo latest change in optics before it causes the beams to be aborted. Additional (optical) output has been added to SVTRAD1.5 to enable this

10. SVTRAD Upgrades M. Bruinsma10Sept. 22nd 2003 Status, Time schedule & commissioning Present status of SVTRAD upgrade: SVTRAD1.5 readout board designed, layout of PCB started First board ready for testing in November SVTRAD-DAC module designed, layout done, PCB being produced. Electronics upgrade has been endorsed by Review Committee (July 23 rd ) Commissioning strategy: 1.Lab tests (November/December) Check contacts, FPGA firmware, calibration with current-source, optimization of temperature corrections, test abort logic, fast history 2.Tests with installed diodes/diamonds (December/January) Connect to BE diodes, routed to electronics hut, separate IOC Long-term stability, check abort decisions, correlate with other sensors 3.Installation in IR2 during access (first replace BE board, then others)

11. SVTRAD Upgrades M. Bruinsma11Sept. 22nd 2003 For more information … Review document: BAD339: "SVT Radiation Protection: Upgrade Requirements & Scenarios" Upgrade website (links to talks, documentation, etc): http://www.slac.stanford.edu/BFROOT/www/Detector/SVT/Operations/SVTRAD/UPGRADE/ Design materials of SVTRAD1.5: http://www.slac.stanford.edu/BFROOT/www/Detector/SVT/Operations/SVTRAD/UPGRADE/ SVTRAD15/SVTRAD15_design.html Design materials of SVTRAD-DAC: http://www.slac.stanford.edu/BFROOT/www/Detector/SVT/Operations/SVTRAD/UPGRADE/ SVTRADDAC/SVTRADDAC_design.html Review materials (talks, etc.): http://www.slac.stanford.edu/BFROOT/www/Detector/SVT/Operations/SVTRAD/UPGRADE/ SVTRAD15_Review_Jul2003/