A Simple Method of Uniformity Measurement and RICH

A Simple Method of Uniformity Measurement and RICH R&D 14. Oct. 2008 C. W. Son* J. KIM, J. G. YI, H. Y. LEE, K. E. Choi, H. D. Son, K. H. Kim In-Kwon Yoo Department of Physics, Pusan National University Heavy Ion Physics Experiment LAB 1

Contents 1. M o t i v a t i o n 2. Uniformity measurement of Multi-anode PMT 3. Mini-RICH test at Poha ng Accelerator Lab 4. Single photoelectron measurement 5. C o n c l u s i o n 2 & O u t l o o k

Motivation : mini-RICH detector - Mini-RICH detector consists of a gas radiator and a concave mirror, a multi-anode PMTube H 8500 by HAMAMATSU 8× 8 PMT (HAMATSU, H 8500) - Multi-anode PMTube has different sensitive -> need Uniformity measurement Sliver coated Al Mirror 3

Motivation : uniformity of MAPMT ※Uniformity - The uniformity is a fundamental characteristic of a photo multiplier. Since each channel has its own dynode-anode system, its sensitivity fluctuates each other. te i u q d n a n o i t a c li p e v m i s o n C expe [ Hamamatsu Method] [HAMAMATSU uniformity] 4

A Simple method Uniformity measurement : light source Diffuser 1 - A simple method Diffuser 2 PMT Diffuser 3 Uniform Light [Blue LED (λ= 472 nm)] Z -> LED and diffuser set - Light Uniformity have a little difference at each point -> take uniform region Diffuser set (x, y, z) = ( 0, 0, 340) Z USB 2000 (x, y, z)=(0, 1000, 375) X X Y Y [light intensity distribution after diffuser] 5

Multi-Anode Photomultiplier tube H 8711 H 8500 Pixel 4*4 Pixel 8*8 Effective area [mm 2] 18. 1*18. 1 Effective area [mm 2] 49*49 6

Result of Uniformity measurement [64 pixel MAPMT] [16 pixel MAPMT] Norm alize d 7

RICH test at PAL - Pohang Accelerator Lab -> 60 Me. V/c electron - Our gas system consists of a compress and an air tank , regulator - We used nitrogen gas -> Nitrogen gas more effect rather than air which have moisture RICH 60 Mev/c [Beam line] [RICH align] 8 [Gas system]

Result of mini-RICH Before correction After correction(our uniformity) After correction(HAMAMATSU) - Before correction, central region is high - Ring image show up by uniformity correction 9

Photoelectron measurement and result Diffuser 1 Diffuser 2 Polarizer 2 PMT Diffuser 3 Polarizer 1 - Two polarizer to attenuate light intensity - Calculate photoelectron of Uniformity measurement -> [QDC channel(uniformity)] /[QDC channel(SPE)] 10

Conclusion & Outlook Conclusion New diffuser method for uniformity and single photoelectron measurement -> quite well Outlook 1) Single photon electron measurement for 64 Channel MAPMT 2) 2 nd mini-RICH - Longer Radiator length - Larger acceptance Mirror (size↑, UV range reflectivity↑) - UV-extended window MAPMT 11