DØ Radmon status 26/08/99 Sijbrand de Jong/Bram Wijngaarden/Silke Duensing Contents:  What is to be monitored and what actions to take ?  Historical setting: CDF and OPAL  The solutions chosen  Status of preparation  Time table  Summary and Outlook

What is to be monitored:  Instantaneous radiation levels:   at millisecond time scales   at seconds time scale   at minutes time scale   at days/months/years time scale  Sensitivity:   rad/hour (long term)   rad/second (short term/bursts)

Action: Beam abort  High Instantaneous radiation levels:   at millisecond-seconds time scales   rad/second levels Integrate the radiation with a running few seconds integration time and fast rise time (allow abort as fast as in 1 millisecond if the times get rough) Absolute reliability: implement in hardware and failsafe, also reliable monitoring (to test reliability and to justify a posteriori)

History part I: CDF CDF already has a monitor and beam abort system:  Beam Loss Monitors (BLMs):   1 Atm. Ar filled glass/Al tubes Current  Radiation / low sensitivity   TLDs infrequent access at long intervals Used to gauge the BLMs a posteriori Will use same system in RUN II, but at larger z distance (and the distance was already large…)

History part I: CDF  DØ BLM proven to be reliable, Beams division trusts them … use them also for DØ Bulky: use at large z distance, 4 on each side of DØ I.P.

Drawbacks:   At large distance from point of interest (SMD)   Limited sensitivity: no low dose / long term integral But:   Can use for beam abort (only low sensitivity needed, trusted by beams division)  :  Gauge with a second sensitive system near SMD :

Status BLMs available/delivered from Beams division The mounting of the tubes in principle decided (the drawing has to be cleaned up, then production can start) HV and signal cables per (long) coax cables (5 cables per side: 1 HV (4 tubes daisy-chained) and 4 signal cables)

History part II: OPAL All 4 LEP experiments have good radiation monitoring and beam abort systems, the OPAL system is used as inspiration for DØ. Principle: ~1 cm 2 Si diode current  radiation Two gain ranges (a la OPAL) to accommodate high sensitivity fast measurement and lower sensitivity long term integral measurement Maintain fast signals to the external electronics

Location of the sensors in DØ: F-disk H-disk

The sensor modules

Sensor module description I Wedge-shaped modules of flex print laminated onto thin Beryllium support/cooling plates Mount on F- & H-disk support rings between wedges Flex print ends in flex cable that feeds through the CF support tube (F-disk) and connects to traditional cable bundle using a small PCB with an Hirose connector The unshielded cable part is to be kept as short as possible Be plates keep Si diodes significantly colder than the strip detectors

Sensor module description II Pre-amp electronics with two gains to be transmitted to the outside world Rad hard electronics Low power dissipation Fast signal, allowing to capture single beam crossings if desired (this is not really foreseen in the standard mode of operation, but can be quite useful to calibrate the system using single MIPs)

Choice of dynamic range The design allows to change the dynamic range, within reasonable limits, by changing one or two discrete (smd) components Current choice: Low gain 3 V  400 Rad/second High gain 3 V  225 Rad/hour (These are sustained voltages-rates) The rise- and shaping-time are fixed. The shaping-time is a few hundred ns, the rise- time much faster

More design choices A leakage current compensation can be set externally (remotely) The circuit is tested to 400 V bias voltage and is protected against a short over the Si diode(s)

Status Sensor module prototyped and final circuit decided Be plates dimensions fixed and ordered F-disk H-disk width at top 0.866”/22mm 0.866”/22mm width at bottom 0.394”/10mm 0.472”/12mm total length 4.082”/103.68mm 4.496”/114.2mm top part length 1.535”/39mm 1.535”/39mm Flex circuit order pending understanding of the length of the flex cable part (distance of connector from the circuit)

Si diodes sensor module prototype Correct dimensions for F-disk 2 layouts tested (one better than other: choice made) Design allows to cover with EM shielding foil

Si diodes Test structure from H-disk wafers 48 diodes with and 48 diodes without guard ring in hand setting up I-V, C-V (depletion voltage) and leakage current tests at University of Nijmegen  select the best for mounting on modules

Cabling  BLMs: coax cables all the way to receiver electronics. Need a break at the end of the muon shield.  Diodes: short flex cable, then “round” cable to patch panel between barrel and end cap CAL, then more robust round cables to receiver electronics. Signal as fine group shielded twisted pair and power cables bundled together with common electrical and mechanical shield.

Cabling: open questions  Lengths of flex cable ?  Length of conventional cable parts ?  Types of conventional cables that may be used (safety/”standard cable”/…) ?  Patch panels: available size/… ?  Location of receiver electronics ?

Readout  VME based (single crate system) using analog receiver, integrator boards, one or more ADC modules and a VME CPU/host  Use Beam division/CDF logarithmic receiver/amplifier for BLMs, use also their scheme to derive beam abort signal  Use linear differential receivers a la OPAL for Si diodes, use parallel streams with different integration time

Readout (continued)  Use cyclic buffer for fast readout (0.1-1ms) and read out on demand (beam abort/warning level/test/…)  Send integrated rates (Rad/sec or Rad/hour) with averages over several seconds-minute to display in control room, store these values once per minute in data base Keep this one VME crate on uninterruptable power or connect to Tevatron power Make sure this crates functions independently from DØ readout/slow controls and monitoring

Readout: open questions  ”Standard” DØ VME ADC module ?  ”Standard” DØ VME CPU module ?  ”Standard” DØ online data base ?  Connection to DØ slow control and monitoring system ?  Presentation in DØ control room ?  Interface to Tevatron (beam abort/monitoring info) ?

Tevatron startup At Tevatron startup (without DØ) provide fully functional system  Test the system  Feed-back information to Tevatron The Si diode sensor modules will be in addition to those installed on the SMD (made as normal PCB) Temporary mounting/support system for BLMs and Si diode sensor modules still to be designed

Schedule ( ) Mid-Sept: Final layout of Si diode sensor modules Final design of BLM support system End-Sept: Final design of temporary support End-Oct: Final design of receiver module electronics Order VME crate, ADC and CPU modules Final and temporary BLM support finished End-Nov: Si diode sensor modules finished (2 sets) End-Dec: Receiver electronics finished (+VME ADC/CPU) End-Jan: Fully functional system around beam line Si diode sensors ready for mounting on F- and H-disk support rings

Summary Two complementary radiation monitoring systems BLMs in hand, mounting design ~completed, manufacturing no problem (at Univ. of Nijmegen) Design of Si front end done and prototyped Design of readout electronics ongoing for both systems (but no particular difficulties foreseen) Work needed on: cabling, interface to DØ and Tevatron Separate system foreseen at Tevatron set-up