LHCb Rich Detectors Control and High Voltage Systems

LHCb Rich Detectors Control and High Voltage Systems Mario Sannino On behalf of LHCb RICH Group Rich 2007 Trieste 19. 10. 2007 1

LHCb Rich Detectors Control and High Voltage Systems • An overview of the Monitoring/Control System of the RICH Detectors in LHCb experiment will be presented • In particular this talk will concentrate on the Monitoring/Control methods fundamental for an efficient RICH Detector operation Rich 2007 Trieste 19. 10. 2007 2

LHCb RICH detectors Mirror Support Panel Flat mirrors Spherical Mirror 8 m Support Structure 4 m Beam pipe Photon detector housing and shielding RICH 1: 2 -60 Ge. V/c Flat Mirror RICH 2: 17 -100 Ge. V/c Rich 2007 Trieste 19. 10. 2007 Central Tube Photon detector housing and magnetic shielding 3

Fundamental for an efficient RICH operation are: • Low Voltage and High Voltage control and monitoring • environment monitoring (temperature, pressure, humidity) • radiator gas quality monitoring • mechanical stability (mirror alignment) monitoring • detector safety This is achieved by means of the DCS (Detector Control System), in charge of detector operation, i. e. Monitoring, Control and low level Safety. DCS will also automatically recover simple problems and restore normal operating conditions. Rich 2007 Trieste 19. 10. 2007 4

LHCb Partial Simplified view ECS = Experiment Control System DCS = Detector Control System DSS = Detector Safety System Rich 2007 Trieste 19. 10. 2007 5

ECS/DCS Hardware Implementation Board level electronics • Electronics in barracks (out of Radiation Area) • Front-ends, Readout Units, • Timing and Fast Control components, • VHV Control – Credit Card PC’s Ethernet interfaced acting as an embedded controller generating needed I 2 C, JTAG and a parallel bus by means of a proper “glue” logic (Glue Card) Ethernet • 66 85 12 mm 3 • Pentium Compatible CPU • Linux/DIM S I 2 C JTAG Bus Credit Card PC Glue-Card 6

ECS/DCS Hardware Implementation Front-End Electronics • In Radiation Areas needed I 2 C and JTAG generated by the busses • SPECS • Serial Protocol (inspired from Atlas) • 10 Mb/s S I 2 C JTAG • Slave is radiation tolerant • CAN protocol (0. 5 Mb/s) in charge of controlling ELMB’s SPECS (used for Environmental and Voltage monitoring) CAN M I 7

Implementation of LHCb RICH Detectors Monitoring Rich 2 ECS supervisor PC Supervisory Level PVSS II (Control Room) Control Level (Counting Room) Rich 2 Voltage and Environment Monitoring Rich 2 Power Supplies Control Rich 2 VHV Power Supplies Control Quality Monitoring Device/Sensor Level PLC ELMBs Radiation Area Sensors T, P, H Voltages LV, HV, L 1 Environmental Monitoring Voltage Monitoring Power Supplies Other (DSS, …) HPD Planes VHV Temp. Safety Interlocks Power Supplies • Gas Quality • Alignment Quality Monitoring • Environmental monitoring is implemented by means of resistive transducers ( (PT 100 &1000 for T, Diaphgram Sensors for Pressure, HMX 2000 -HT sensors for Humidity) • ELMBs are CAN controlled monitoring boards with 64 analog input channel 16 bit res. Rich 2007 Trieste 19. 10. 2007 8

Environmental Parameters Monitoring HPD box temperature Environmental Parameters PVSS II typical Monitoring Panels HPD box humidity RICH 2 CF 4 radiator temperature <- 5 days -> Rich 2007 Trieste 19. 10. 2007 9

Gas Radiator quality Monitoring (I) The Gas Purity is critical to a reliable working of the RICH Detectors. Speed of sound in gases depends on molecular weight: and so it can be exploited to quickly spot gas pollution. g = cp/cv is the ratio of specific heats R is the constant of gases T is the absolute temperature M the molecular weight Effect of air contamination Gas N O air C 4 F 10 CF 4 Molecular weight 28 32 29 238 88 Speed of sound (m/s) at 30 C 354 332 349 ~130 C 4 F 10 CF 4 n 1. 0014 1. 0005 Theta max (mrad) 52. 88 31. 62 1% N 2 qmax 52. 68 (0. 2) 31. 55 (0. 07) 3% N 2 52. 26 (0. 62) 31. 42 (0. 2) Typical error (mrad) 1. 5 0. 6 ~150 Rich 2007 Trieste 19. 10. 2007 10

Gas quality Monitoring (II) Speed of sound is monitored by measuring the time that a sound pulse takes to propagate back and forth along a gas column after having been reflected by the opposite wall. 2 such Systems on each Rich One on gas inlet A second on gas outlet The heart of the system is an electrostatic transducer acting both as source and detector. The time measurement is performed by a National Instrument Acquisition Board with an internal counter running at 20 MHz so, with a resolution of 50 ns This is enough to detect a 1% CO 2 pollution in C 4 F 10 (see graph) 10 11

Laser alignment monitoring system (I) Mirror position must be known with good precision and any change of it must be tracked as accurately as possible. CCDs HPD Plane A 0. 1 mrad resolution is required as seed for final software alignment. Flat Mirror Spherical Mirror An optical system has been implemented in order to monitor changes in selected mirror segments. Working principle: Laser with optical fibre coupling system delivers light to 16 fibres in Rich 2 and 8 fibres in Rich 1. Each fibre has a focusing unit at its end and is focused onto a mirror segment (4 spherical and 4 flat per side). Beam Splitter Focuser Common Mounting Plate Mirror A beam splitter provides a reference beam for each fibre focused on a CCD camera on roof of detector. A second beam reaches the mirror and then is reflected back to the CCD camera. Rich 2007 Trieste 19. 10. 2007 12

Laser alignment monitoring system (II) Can track difference between two beam spots, even if spots move: Accuracy of monitoring better than 0. 01 mrads. 13

VHV Power Supplies Control System (I) In LHCb Rich a custom VHV system for the HPD field supply was needed due to the fact that no commercial power supply satisfied our requirements: • 20 KV output • Ethernet network interface compatible with CERN standard • Reliable and modern (maintenance!) Architecture of the system The system is composed by 3 items: 1. Commercial HV unit: One unit for each column. 2. Motherboard with local intelligence One unit for each Detector 3. Control Board with optical isolation (avoid Gnd loops) One unit for each column Rich 2007 Trieste 19. 10. 2007 14

VHV Power Supplies Control System (II) Rich 2007 Trieste 19. 10. 2007 15

VHV Power Supplies Control System (III) • Commercial HV unit: ISEG CPn 200 504 10 -K – 0 -20 KV output – Imax = 0. 5 m. A – Remote control: analog input 0 -10 V – Possibility to set Imax with a control voltage – Monitoring of Vout and Iout – Reasonably priced – Custom version possible (2 output cable to cope with the HV splitter) Rich 2007 Trieste 19. 10. 2007 16

VHV Power Supplies Control System (IV) The Motherboard • Standard VME size card ( 6 U type) • Local Intelligence: Credit Card PC (CCPC) – Ethernet interface built-in – CERN fully supported – Easily interfaced with external devices by means of the so called Glue Card. Connections with Control Boards implemented by means of 4 I 2 C buses (from the Gluecard) • Interlock Management and distribution entirely controlled by a small FPGA 17

VHV Power Supplies Control System (V) Control Board ISEG VHV Power Supply 17 18

Installation of VHV Rich Power Supplies in LHCb Pit 19

VHV Power Supplies Stability (19540 ± 18) V A stability of the ouput voltage under load of the order of 1 ‰ is achieved as can be seen from the aside plots where a voltage of 19540 V with 20 V RMS max is reported for a sample channel 20

Conclusions In LHCb a complex system in order to control and monitor the Rich Detectors was designed and implemented • All the needed parameters are monitored Ø Environmental ü Pressure ü Temperature ü Humidity Ø Quality ü Mirror Alignment ü Gas Quality • A new VHV Power Supply System completely automatized and remotely controlled was developed and is now working with good performances • In case of simple problems the system is able to recover them restoring normal operations conditions • In case of hard safety problems the system is able to interlock the detector putting it in a safe state. Rich 2007 Trieste 19. 10. 2007 21

Spare Slides Rich 2007 Trieste 19. 10. 2007 22

LHCb RICH detectors RICH 2: 17 -100 Ge. V/c RICH 1: 2 -60 Ge. V/c Rich 2007 Trieste 19. 10. 2007 23

Monitoring • HPD enclosure: – Air temperature (2 pt 100). – Humidity. – Up to 16 temperatures (hot spots) per column (pt 1000). – High Voltage (6 voltages per column). – Cooling pressure. – Light level. – Voltages and currents (from the power supplies). • Temperature in RICH 2 radiator: – 20 pt 100 in gas volume. – Relative pressure (no gas yet). Rich 2007 Trieste 19. 10. 2007 24

Environmental Parameters Monitoring (II) RICH 2 CF 4 radiator temperature Environmental Parameters PVSS II Monitoring Panel Rich 2007 Trieste 19. 10. 2007 25

Safety • PVSS – Per column: • Any high column temperature will switch off the particular column. • Power supplies will trip at over current. • HV disable if over-current, over/under-voltage, monitoring problem. – Per HPD enclosure: • High ambient temperature will switch off whole side. • Loss of cooling will switch off whole side. • DSS – Any alarm switches off whole RICH detector. • Ambient temperature sensors. • Chain of thermo-switches (1 per column). • Rack related alarms. • Light level – Disables High voltage. Rich 2007 Trieste 19. 10. 2007 26

An embedded PC is still not a board-controller • For controlling, configuring and monitoring FPGAs and ASICS need rather I 2 C, JTAG Traditional PC interfaces: PCI, ISA, parallel port, USB not very suitable for chip-control • and a high-speed, “simple”, long distance parallel bus • Need some small adapter or “glue-”logic • The LHCb glue-card has an I 2 C / FPGA controller + a fast local bus generated from a PLX 9030 all controlled by an FPGA. (For details see: F. Fontanelli, B. Jost, G. Mini`, N. Neufeld, R. Abdel. Rahman, K. Rolli, M. Sannino 10 th ICALEPS Conference Geneva 2005 PO 2. 062) Rich 2007 Trieste 19. 10. 2007 27

Laser alignment monitoring system (Ib) q Analysis software needs to recover centre position of reference and reflected beam with optimum accuracy and robustness. q Beam not perfectly Gaussian so fitting method is not appropriate for a variety of differently shaped beams q Adopt a different approach using techniques borrowed from image processing. q Adopt a multi stage approach: 1. Smoothing filter 2. Edge enhancement 3. Sobel mask edge detection 4. Hough transform accumulator to determine centre of beam 5. Anomaly cut for spurious centre elimination 6. Centre spot location mask 7. Weighted average for centre determination. Rich 2007 Trieste 19. 10. 2007 28

Voltages Monitoring Rich Voltages Monitoring Panel Rich 2007 Trieste 19. 10. 2007 29