1. Measurement of 'intrinsic' properties of scintillating fibers H. Sakamoto Osaka University, Japan A.Sato M. Yoshida Y. Kuno Osaka Univ. K. Yoshimura KEK

2. Purpose To optimize a concentration of the secondary dopant (3HF) for scintillating fibers KEK beam test to study light yields & cross talk for some different concentration Attenuation length of a clear fiber Light yield loss Summary

3. Tracker for MICE Measuring the emittance of muon beam by reconstructing the beam with position detectors in the magnetic field Requirements Measuring the emittance with accuracy of 0.1% each plane is within 0.4% radiation length to restrain multiple scattering Working stably in a high back ground from RF cavity Scintillating fiber (Sci-fi) tracker

4. Sci-fi tracker 30cm Edge of layer Requirements for scintillating fiber Diameter ： 350um No cross talk Small light yield due to small fiber High Q.E. photo detector VLPC (Visible Light Photon Counter ） Sensitive region ～ 500nm ３ HF fiber mixed with wavelength shifter To the photo detector Clear fiber Sci-fi station Layout of Sci-fi station

5. Beam test @ KEK To study the light yields and cross talk of 3HF concentration dependence Scintillating fibers tested: Kuraray SCSF-3HF ; 350um-phi, multi-clad, s-type Primary (pT) + Secondary (3HF;5000ppm) Primary (pT) + Secondary (3HF;3500ppm) Primary (pT) + Secondary (3HF;2500ppm) No primary + Secondary (3HF;5000ppm)

6. KEK beam test set up Ⅰ D1 TOF2 D2 Sci-Fi Trigger coincidence of all counters and Sci-Fi Data we took ADC & TDC of all counters and Sci-Fi 3m 0.5m 5m 600MeV/c 700MeV/c 1Gev/c TOF2 Sci-Fi TOF1 D1 Dark box D2 p + π + μ + Beam

7. Beam line Sci-Fi in Dark box D1 D2 TOF2 KEK beam test set up Ⅱ

8. 3HF emission spectrum & Q.E. of VLPC 3HF emission spectrum 520nm Quantum efficiency of VLPC 520nm

9. Photo multiplier tube We used the photo multiplier tube instead of VLPC.  Hamamatsu R7899MOD Extended Green Photocathode 1 inch diameter 10 stage Head-on Type Prismatic Window HV= -1800V

10. Set up of scintillating fiber Side view PMT Sci-Fi Aluminized tape 22mm 20 fibers These were in a dark box Front view PMT Sci-fi

11. Analysis Average number of photo electron was estimated by fitting the sci-fi ADC spectrum to a poisson distribution. typical sci-fi ADC spectrum Adc count count

12. Result of light yield 5000ppm has the highest light yield in tested fibers (2.6p.e.@MIP). Light yield of 3HF concentration dependence Ave. # of p.e. dE/d ｘ (MeV/cm) 5000ppm 3500ppm 2500ppm Only 5000ppm 350um phi

13. Set up for cross talk test The differences A & B of light yield result in cross talk Black papers between every fiber Tie together every two fibersPut black papers in between A B

14. Result of cross talk test Cross talk Ave. # of p.e.@MIP (2.0 MeV/cm)p.e.@MIP 5000ppm3500ppm2500ppm Only 5000ppm Set up A2.602.24 1.86 Set up B2.782.372.312.00 (B-A) /A7%6%3%8% No evidence of cross talk If cross talk small large very small

15. Conclusion from the beam test We tested scintillating fibers of different 3HF concentration. We used green sensitive PMTs in stead of VLPC. The result of light yield test 5000ppm has the highest light yield of 2.6 p.e. @ MIP. The result of cross talk test No evidence of cross talk can be seen.

16. Atte. length of clear fiber Ⅰ Set up Clear fiber: KURARAY CLEAR-PS Round, Multi-Clad, S-type Pulser: Duration: 1nsec Period: 10msec Pulse height: -5.5V Silicon photo diode ORIEL Model 70313

17. Atte. length of clear fiber Ⅱ Fitting F=exp(A-x/L1)+exp(B-x/L2) Result A =1.49 B =0.32 L1=7.62 L2=0.69 Attenuation Length is 7.62m. Our waveguide of prototype is 4m clear fiber 40% loss was estimated KURARAY CLEAR-PS 1.05mmphi, Multi-Clad, S-type, Round

18. Summary We studied the light yield and cross talk of scintillation fibers mixed with 3HF as a secondary dopant. Scintillating fibers tested ： Kuraray SCSF-3HF pT+5000ppm, pT+3500ppm, pT+2500ppm, only5000ppm Light yield : pT+5000ppm has the highest light yield of 2.6 p.e.@M.I.P.p.e.@M.I.P Cross talk : No evidence of cross talk can be seen. We also studied the attenuation length of the clear fiber. 40% loss was estimated in 4m (in the prototype)