1. SksMinus status 01 HB meeting 2008/4/1 白鳥昂太郎

2. Contents  Target : 4 He target  Aerogel Cherenkov counters : SAC  Hyperball-J efficiency

3. 4 He target Designed by Ishimoto-san

4. Plan  Optimize Target length : < 300 mm (as short as possible) Target shape : Cylinder → Elliptic cylinder, material selection Arm design : To avoid SAC, BAC, HBJ frame  Test Cooling test by refrigerator Existent vacuum chamber with the same arm length

5. AC design Index : n=1.03 ~4 photons  BAC1,2 160×30×70 mm  SAC1 : 250×80×70 mm  SAC2 : 320×90×70 mm With 2 inch fine mesh PMT  ~72 mm)×8 Inside : White box, w/ or w/o reflector It is necessary to design realistic one!

6. Discussion  Double stage SAC or SAC+SFV ? 7  Li 692 keV yield by SAC+SFV (Master thesis) 9.5 counts/hour → 8.7 counts/hour (0-20°) : 8 %↓ 5.3 counts/hour → 4.6 counts/hour (0-8°) : 14%↓ SFV size is too large. (Not optimized) SAC efficiency has to be more than 96%.  - detection efficiency by the double stage SAC is 92%.

7. Hyperball-J efficiency  Total photo peak efficiency @ 1 MeV  ray Original Point source : 6.1% Uniform source : 6.0% Modified Point source : 5.7% Uniform source : 5.7% W/o Target, BAC and SAC material