Proposal Summary

1. Radiation Damage Studies for the PHENIX Forward Silicon Vertex DetectorMelynda Brooks, Matt Durham, Hubert van Hecke

2. Proposal Summary • LANL-led silicon detector project (FVTX) installed into RHIC this FY, 4.5 cm from beam pipe • Increased leakage current in detectors implies somewhat larger radiation doses than were anticipated, profile is different from expected (radiation sources are not entirely from primary collisions) • We need to determine the expected lifetime of the detector given the doses that were measured this year • We may also want to propose some shielding before next RHIC run (Jan. 2013) • These particular sensors have never been fully characterized against dose • We would like to irradiate a series of sensors to varying levels and measure how the performance changes versus dose. (I-V in-situ, more detailed measurements offline) • Total dose required is ~1013 • Expect that ~1 day of beam time will be • sufficient – most of the time needed for setup, • putting in/pulling out sensors as they get • irradiated.

3. The PHENIX Detector • FVTX Project • Adds precision tracking to the interaction point • Measuring quark + gluon properties in the only laboratory that provides them in unbound state (Quark Gluon Plasma) • Constructed FY08-FY11, collected 1st data FY12 • RHIC Provides many beam species: • 200 GeV: p+pd+Au, Cu+Cu, Cu+Au, Au+Au, U+U • 500 GeVp+p • Lower energy everything • p+p is highest luminosity FVTX Detector

4. FVTX Event Display – 510 GeVp+p Low multiplicity, but high interaction rate  largest particle dose to detector

5. FVTX Event Display – 200 GeVU+U High multiplicity, but low interaction rate  lowest particle dose to detector

6. Radiation Damage I • As expected, we see a steady increase of leakage current versus time in beam • Unfortunately, the increase is faster than we expected • Possibly due to backgrounds induced in our magnet 500 GeVp+p U+U 200 GeVp+p • Damage is also largest for sensors farthest from the interaction region – also indicates magnet region contributes • The projected current draw should not be a problem, but the effects on I-V changes, sensor noise, efficiency have not been quantified for these sensors

7. Radiation Damage II • Two test sensors were placed near the magnet structure during 500 GeVp+p beam running at RHIC • One was shielded with 5 cm of borated polyethelyene Unshielded Shielded If tests show it is necessary, permanent shielding might be added to the apparatus at PHENIX during this year’s RHIC shutdown.

8. Proposal • The fluence received by the FVTX in a typical year at RHIC is equivalent to ~ 1011/cm2 protons at 800 MeV • We would like to expose ~six FVTX silicon sensors to 10 years+ equivalent radiation dose, in ~5x1011 increments. • At each interval, an I-V curve will be measured for each wedge and one of the wedges removed from irradiation. • Offline we will further characterize the detector performances of the sensors that were removed during middle of irradiation • Total requested time in Blue Room is 1 day. • We would like to have beam time early in the schedule in case we need to make any modifications to RHIC setup before RHIC beam start-up (January 2013 beam, close-up starts in fall 2012) • If possible, we welcome collaboration with other users with similar experimental goals.

9. Backups

10. FVTX Overview • Two Arms, Four tracking stations with full azimuthal coverage • 75 m pitch strips in radial direction, 3.75° staggered phi strips • Radiation length < 2.4%/wedge to minimize multiple scattering • Located ~20cm from nominal interaction point • Occupany in central Au+Au <3% • Initial funding through LANL LDRD, construction funding from DOE 22 mm

11. Installed December 2011