1. Diamonds in CDF Peter Dong, UCLA Ricardo Eusebi, FNAL Anna Sfyrla, Geneva Rick Tesarek, FNAL Rainer Wallny, UCLA With much help from Jonathan Lewis (FNAL) and the PPD EE Department Silicon Workshop II Friday, May 12, 2006

2. 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)

3. Properties of diamond SiliconDiamond Band gap [eV]1.125.45 Electron mobility [cm 2 /Vs]14502200 Hole mobility [cm 2 /Vs]5001600 Saturation velocity [cm/s]0.8x10 7 2x10 7 Breakdown field [V/m]3x10 5 2.2x10 7 Resistivity [Ω cm]2x10 5 >10 13 Dielectric constant11.95.7 Displacement energy [eV]13-2043 e-h creation energy [eV]3.613 Average e-h pairs per MIP per μm8936 Charge coll. dist. [μm]full~250 Low I leakage, shot noise Fast signal collection Low capacitance, noise High radiation hardness Smaller signals

4. 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.

5. 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.

6. Typical Shot Setup Final proton injection (36 bunches) ramping scraping collisions 9 pbar transfers

7. Readout Electronics HV card (4 channels) Digitizer card FE CPU Timing 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

8. Our Diamonds West low- beta quad West BLMs E1, just downstream of E0 collimator 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.

9. What can we see? Quench at B0 DiamondsBLM Collimator move during scraping

10. 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.

11. The new diamonds West side East side The installation crew

12. 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.

13. 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.