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.