Diamonds in CDF
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Transcript of Diamonds in CDF
Diamonds in CDFPeter Dong, UCLA
Ricardo Eusebi, FNAL Anna Sfyrla, GenevaRick Tesarek, FNAL
Rainer Wallny, UCLAWith much help from Jonathan Lewis (FNAL) and the PPD EE
Department
Silicon Workshop IIFriday, May 12, 2006
Why do we want diamonds?
Beam incidents can damage the silicon. We need to monitor the radiation field so
we can pull an abort if the beam becomes unstable.
Our present radiation monitoring has drawbacks: Loss counters: far from the silicon BLMs: slow response with current electronics PIN diodes: passive monitors (cannot be used
for an abort)
Properties of diamond
Silicon Diamond
Band gap [eV] 1.12 5.45
Electron mobility [cm2/Vs] 1450 2200
Hole mobility [cm2/Vs] 500 1600
Saturation velocity [cm/s] 0.8x107 2x107
Breakdown field [V/m] 3x105 2.2x107
Resistivity [Ω cm] 2x105 >1013
Dielectric constant 11.9 5.7
Displacement energy [eV] 13-20 43
e-h creation energy [eV] 3.6 13
Average e-h pairs per MIP per μm 89 36
Charge coll. dist. [μm] full ~250
Low Ileakage, shot noise
Fast signal collection
Low capacitance, noise
High radiation hardness
Smaller signals
Why we want diamonds
In short, diamonds are Small – they can fit almost anywhere Fast – their response time is very short Hard – they will remain essentially unaffected by
radiation at the Tevatron. This means they can sit very close to the
silicon, never have to worry about radiation damage, and can pull an abort very quickly.
BaBar and Belle already have diamond systems; CMS and ATLAS will install them as well. CDF is the first hadron collider detector to use diamonds.
Our first diamond
In August 2004 we installed a diamond in the east plug.
It was read out at ~8Hz by a Keithley electrometer over ~100 feet of cable on the first floor in B0.
After irradiation, we saw a leakage current of ~200 pA (from ~1 pA).
Signal during normal store ~1 nA.
Typical Shot Setup
Final proton injection(36 bunches)
ramping
scraping
collisions
9 pbar transfers
Readout Electronics
HV card(4 channels)
Digitizer cardFE CPUTiming Card
Use readout system for Tevatron BLM electronics upgrade
Installed this shutdown Digitizer
4 channels with integrator and ADC Generates primary abort signals Runs at 20 s – slower than intrinsic
signal formation time of diamond, but it’s the best we can do for now
Timing Card Synchronizes digitizers Latches control signals
Abort Concentrator Controls masking and multiplicity of
inputs from digitizer Controller
Interface to VME for crates with abort High Voltage
Up to 2.25 kV – use voltage divider to get 500V (and prevent accidental application of too much voltage)
Front-End CPU MVME 2xxx: Acnet interface, etc. Electronics designed
by Accelerator Division EE department
Our Diamonds
West low-West low-beta beta quadquad
West West BLMsBLMs
E1, just E1, just downstreadownstrea
m of E0 m of E0 collimatorcollimator
In November 2005, while the Tevatron was shut down for repairs, we installed three more diamonds in CDF and one in the Tevatron. These diamonds have since been removed.
What can we see?Quench at B0
DiamondsDiamonds BLMBLM
Collimator move during scraping
The full diamond system
Installed four diamonds on each side of the tracking volume.
Mounted on a plastic support structure that clamps onto the beampipe, putting diamonds at a radius of ~2 cm.
Connected to triaxial cables (colored yellow for easy identification) that penetrate the silicon baggie and the foam.
Read out in a crate on the first floor.
The new diamonds
West side
East side
The installation crew
The next step
We’ve installed all the diamonds, tested them with a source, and checked all the cables from the first floor.
Need to install the crate, get the hardware and software working.
When the beam turns on, then the real testing begins.
Once the behavior of the diamonds is understood, we can look at implementing abort functionality.
Conclusion
Our diamond detectors are real-time radiation monitors in the tracking volume.
We now have eight diamonds installed in CDF, and are in the process of commissioning them.
These should allow faster response to beam incidents and better protection of the silicon.