KEK BT Summary &Plan Shinshu University Miho Nishiyama

KEK Fuji beam line ・ Electron beam ・ This beam is made form bremsstrahlung photons from KEKB ring ・ Beam spot size: ~ 3cm x 4 cm ・ Beam energy : 3 GeV ・ Rate: 3 GeV beam

Setup Semiconductor Tracker (borrowed by ATLAS Group) 12cm×6cm Resolution vertical : 23μm horizontal: 580μm Veto counter Beam e - Scintillator Fiber Tracker Trigger counters Movable stage Scintillator strips scintillator Beam e - Semiconductor Tracker Scintillator Fiber Tracker Scintillator strips Movable stage Veto counter Scintillator Setup of side view

A B C D E F beam Scintillator Strips MethodRead- out Cover Thickness (mm) A1 Extruded Fiber TiO 2 3 No fiber ! A2good positioning B1 Reflector big hole B2matched hole C1DirectTiO 2 D Kuraray Direct Reflector 2 E 3 FFiber reference 8 layers with different types of strips 4 same type strips per one layer

All collected events MIP events Response for MIP extruded TiO 2 No fiber extruded TiO 2 good matching extruded reflector bad matching extruded reflector good matching extruded TiO 2 Kuraray reflector Kuraray reflector thickness:2mm Kuraray reflector reference Number of events (log scale) Signal (ADC counts)

Response for MIP Variation of strip by strip Number of events (log scale) Signal (ADC counts) All collected events MIP events Extruded scintillator strip ＋ reflector film good matching These plots show the variation of strip by strip is big. There are 4 results since we’ve prepared 4 strips read out per one layer.

Uniformity extruded TiO 2 No fiber extruded TiO 2 good matching extruded reflector bad matching extruded reflector good matching extruded TiO 2 Kuraray reflector thickness:2mm Kuraray reflector Kuraray reflector reference Beam position (mm) Signal (ADC counts)

Beam position (mm)Signal (ADC counts) Uniformity Variation of strip by strip Extruded scintilattor strip ＋ reflector film good matching These plots show the variations of the uniformity aren’t so big. However light yields aren’t same.

Signal (ADC counts) Beam position (mm) Direct Photon 25% 1mm 1mmφ Direct Photon 100% 1mm Direct Photon 25% 4.5cm 0.4cm 1cm Scintillator strip Sensitive area of MPPC Fiber Problems were found at KEK BT ・ Direct photons caused significant non-uniformity. MPPC

Conclusion The position of fiber and MPPC is important. →We asked KNU to make extruded scintillator strips with the precise size of fiber hole and position. Reflector film works better than TiO 2. →We asked KNU to make scintiilator stirip without TiO 2. Direct photons may cause significant non-uniformity. →Bench test has been done.

Setup PMT Discriminator Gate Generator 90 Sr MPPC ADC (V bias = 76.5 [ V]) Trigger scintillator Thermostatic chamber (25 ℃ ) Extruded with TiO 2 Collimator with 2 mm  hole Signal input Gate input AMP (x63) 72 [ns] KIMOTO reflector Position of  -ray source × x mm MPPC 57mm

Measurement of 3 ways 1mmφ White paint to shield direct light KIMOTO reflector to shield direct light Scintillator with TiO 2 Nothing to shield direct light the length of fiber : 43mm Fiber : 57mmFiber : 43mm

Result of measurement Fiber : 43mm Fiber : 57mm ＋ KIMOTO reflector Fiber : 43mm ＋ white paint MPPC side

To look into two peaks… Check the response for MIP of MPPC side and another. 4.5cm 1cm MPPC side Another side extruded TiO 2 Good matching extruded reflector film Good matching

Response for MIP Number of events (log scale) Signal (ADC counts) MIP events MIP events (MPPC side) MIP events (another side) extruded TiO 2 extruded TiO 2 Good matching extruded Reflector film Bad matching extruded Reflector film Good matching extruded TiO 2 Kuraray(2mm) Kuraray(3mm)

Plan Two peak (~January) Comparison of absolute light yield (~March) Bias voltage dependence (~March)

Back up

MIP selection MIP selected strip spacer Only pedestal signal For the selected strip, MIP event must satisfy following conditions: ・ In the same layer, strips show the pedestal signal but the selected strip. ・ In the front and the rear layer, the strips at same position of the selected strip show the MIP signal. MIP signal e-e-