Optical System for MicroBooNE Arati Prakash Massachusetts Institute of Technology Fermi National Accelerator Laboratory

Outline Introduction - What is MicroBooNE Light in Liquid Argon MicroBooNE PMT System Design Arati Prakash INSS 07/20/2011

Outline Introduction - What is MicroBooNE Light in Liquid Argon MicroBooNE PMT System Design Arati Prakash INSS 07/20/2011

MicroBooNE Experiment 170 ton Liquid Argon Time Projection Chamber (LArTPC) Examine low energy neutrino cross sections Low energy excess observed in MiniBooNE experiment –  or e? Start taking data early 2014 Located on axis to the ~1GeV Booster Neutrino Beamline at Fermilab (Chicago, IL) Arati Prakash INSS 07/20/2011

MicroBooNE Detector Design LArTPC: 3 wire planes with 2.5m drift in 170 tons of LAr Located in a cylindrical cryostat vessel: 4m radius x 12 m length PMT system sits along the wall behind the TPC Charge drifts to the TPC planes T~ms PMT scintillation light detected T ~ns So, the PMT system in principle can trigger the TPC Arati Prakash INSS 07/20/2011

Outline Introduction - What is MicroBooNE Light in Liquid Argon MicroBooNE PMT System Design Arati Prakash INSS 07/20/2011

LAr Scintillation Light Prompt component: T ~ 6 ns (25%) Excited molecule Ar Excitation 128 nm Ar2* Ar* Ar Ar Ar+ Ar2+ Ar2* Ionization Ionized molecule e- Delayed component: T ~1.6 us (75%) Arati Prakash Recombination INSS 07/20/2011

Outline Introduction - What is MicroBooNE Light in Liquid Argon MicroBooNE PMT System Design Arati Prakash INSS 07/20/2011

System Requirements In the MicroBooNE E = 500 V/cm, we expect 24,000 photons/MeV Need to trigger on a 40 MeV proton (~30MeV MIP particles) for MicroBooNE Further goal: trigger on a 5 MeV electron to see supernovae events Arati Prakash INSS 07/20/2011

Design Constraints PMTs must work efficiently at cryogenic temp (87K) UV light does not pass through glass - Scintillation light (128nm) must be made visible to PMTs Optimize Cost vs. coverage Maintain LAr purity Allow enough space for TPC Longevity of the System Arati Prakash INSS 07/20/2011

Choice of PMT 30 x 8-inch, 14-stage Hamamatsu cryogenic PMT Gain ~10^9 Actual gain of the tubes will decrease at cryogenic temperatures and at operating voltages lower than the nominal 1700 V, which are a necessary precaution in order to reduce the risk of high-voltage breakdown in the region where the cabling passes through gaseous argon. With these combined effects, gain still remains above 107. Arati Prakash INSS 07/20/2011

Wavelength shifting Scintillation light is produced in the UV ~128nm. We coat acrylic plates with TPB mixture to shift the light into the visible, ~425 nm. (Previous experiments (ICARUS) coated PMTs directly.) Arati Prakash INSS 07/20/2011

Conclusion MicroBooNE will hopefully provide valuable information for LArTPC detector R&D, as well as data that will be informative for understanding the MiniBooNE observed excess etc. Come see my poster! Thank You Arati Prakash INSS 07/20/2011

MicroBooNE People Arati Prakash INSS 07/20/2011 Brookhaven Lab Hucheng Chen Jason Farrell Francesco Lanni David Lissauer Don Makowiecki Joseph Mead Susan Duffin Veljko Radeka Sergio Rescia Jack Sondericker Craig Thorn Bo Yu Kuo-Chen Wu Princeton University Kirk McDonald Changguo Lu Qing He Columbia University Leslie Camilleri Rachel Carr Gary Cheng Georgia Karagiorgi Camillo Mariani Bill Seligman Mike Shaevitz Bill Willis Bill Sippach Cheng-Yi Chi Los Alamos National Laboratory Gerry Garvey Jackie Gonzales Bill Louis Chris Mauger Geoff Mills Zarko Pavlovic Richard Van de Water Hywel White Fermilab Bruce Baller Cat James Hans Jostlein Stephen Pordes Gina Rameika Jennifer Raaf Tinjun Yang Brian Rebel Rich Schmitt Dave Schmitz Jin-Yuan Wu Sam Zeller Herb Greenlee Mike Kirby Kansas State Tim Bolton David McKee Glenn Horton-Smith MIT William Barletta Len Bugel Janet M. Conrad Christina Ignarra Ben Jones Teppei Katori Tess Smidt Arati Prakash Michigan State Carl Bromberg Dan Edmunds Saint Mary's University of Minnesota Paul Nienaber Syracuse University Mitch Soderberg Yale Bonnie T. Fleming Eric Church Roxanne Guenette Andrzej Szelc Josh Spitz Kinga Partyka Adam Patch Ellen Klein Joseph Lozier Cincinnati Randy Johnson University of Texas at Austin Sacha Kopp Karol Lang Arati Prakash INSS 07/20/2011