1. Detector for the After Proton Measurement M. Aoki

2. After-Proton Detector

3. Scattered Particles to 3NBT Mistakenly used 3-GeV/c protons instead of T=3-GeV protons. But the difference should not be large. protons neutrons Pi+ Pi- gamma Mu- Mu+ e- e+e+

4. Scattered Particles to BLM BLM1*BLM2 = 100% protons T(proton) ~ 2.5 GeV protons neutrons Pi+ Pi- gamma Mu- Mu+ e- e+e+

5. A slide by K. Yamamoto for PAC 2011.

6. Waveforms from BLMs Trigger from a RCS timing sequencer.

7. Waveform Analysis Waveform of the kicker noise is fairly stable. – > Template of the kicker-noise waveform. Subtract the template Extract TDC and ADC information form the waveform Take coincidence between two BLMs. Calibrate hit timing with the extraction timing.

8. Pre-Extraction Region Extraction Region After-Proton Region Mu-e Window

9. Absorber No Absorber – BLM Hits: 109 – (0.217--0.219)e-3 – No of Extractions: 1.48834e7 – BLM/2us = 7.3e-6 1-cm Al (ε=0.0001 for 5-MeV e - ) – BLM Hits: 5 – (0.216--0.218)e-3 – No of Extractions:7.9e6 – BLM/2us = 6.3e-7 1/12 reduction of the constant part. – Low-E Beta-decay BG?? No. of Pulses Low stat. data

10. --------------------------------------------------------------------------------------------------------- Target Radioisotope half-life Production Reaction Q value --------------------------------------------------------------------------------------------------------- Plastic 3 H 12.2y spallation Q-=18 keV 36 Cl 3×10 5 y 35 Cl(n,γ) Q-=709 keV Al 14 C 573Oy 14 N(n,p), 17 O(n,a),spallation Q-=156 keV 22 Na 2.6 y spallation, 23 Na(r,n) Q+=1.8 MeV 26 Al 8×10 5 y 27 Al(r,n) Q+=2.98 MeV Iron, SUS 46 Sc 84d spallation Q-=2.37 MeV 44 Ti 48y spallation QEC=267 keV 54 Mn 312d 54 Fe(n,p), 55 Mn(r,n) Q-=697 keV 55 Fe 2.94y 54 Fe(r,n), 56 Fe(r,n) QEC=231 keV 56 Co 77d 56 Fe(p,n) Q+=3.54 MeV 57 Co 270d 56 Fe(p,r), 58 Ni(r,p) QEC=836 keV 58 Co 72d 59 Co(r,n) Q+=1.3 MeV 60 Co 5.27y 59 Co(n,r), 60 Ni(n,p) Q-=2.8 MeV 63 Ni 92y 62 Ni(n,r) Q-=67 keV Cu 65 Zn 245d 65 Cu(q,n) Q+=330 keV Conclusion: Q < 5 MeV T. Shibata, Radioisotopes 48(3), 208-215(1999)

11. Environmental BG Just before the injection to RCS (so-called “beam head”), no-Al – BLM Hits: 35 – (0--0.25)e-3 – No of Extractions:9.6e5 – BLM/2us = 2.9e-7 Half of the constant BG level. If the BG in the previous plot is from beta emitter, why the rate is so small here? Short- lived beta emitter? Are these low-E beta BG? – Need beam-head run with Al Beam head

12. Pre-Extraction Region Peaks in every 600-ns. At least for 200 us time range. Scattered particles from the filled- bunches. – 5e4 hits per pulse for 1.5e7 extractions- observed. – 200 kW RCS operation No. of p in a bunch = 8e12 – P[BLM hits] = 1/2.8e15 P[e- in mu-e region/3-Gev on target] = 3e-7 (Geant4) 1e5 spectrometer-hits for 2e7 s of run. – Experimental value of P[AP-BG/BLM-hits] – Momentum spectrum of prompt e -.

13. Extraction Region BLM hits by transverse halo – P = 1e-15 BLM hits by longitudinal halo. By combining the kicker excitation curve, the direction of proton orbit that hits the BLM can be obtained. Amount of longitudinal halo can be also obtained.

14. After-Proton Region Life time = 1/p0 = (2.38+-0.20)e-6 sec: consistent with the muon life. – chi2/ndf = 238.2/560: good Constant component = p2 = 0.13+-0.02 /bin – Bin width = 50 nsec: 40 bins/2usec – 6 hits/2usec R AP = ( 6 * 39.5) / ( 1.567e7 * 200 kW / 3 GeV / 1.6e-19 / 25 ) < 9e-19 Issues – How to justify taking the constant part? – Are these “muon-life” components really muons? Including the “muon-life” components: R AP < 3.6e-17 – Non-proton components should be reduced. Maximum Likelihood Include zero bins

15. Upgrade of the Detector 10-cm Iron – Counter efficiencies are almost the same if the kinetic energy of p > 1 GeV. – Counter efficiencies for Michel positrons will be reduced by factor 23. 20-cm Iron – Michel positron reduction: 51 -> no significant improvement over 10-cm case. 10-cm Iron will provide – R AP < 1.7e-18 (currently R AP < 3.9e-17) proton positron

17. Upgrade (2) Need to reduce measured-R AP below 1e-18. BLM hits are all protons in MC. Need “Particle Identification” in reality. Distinguish between protons T>1 GeV and – Low energy beta rays. – <100 MeV Michel positrons. – Gamma rays (promptly produced by whatever).

18. Upgrade (3) Calorimeter – To absorb 52-MeV positrons: Pb 50 mm – To produce >50 MeV dE by 3-GeV protons: Scintillator > 25 g/cm 2 – (Pb(2 mm) + Scintillator(10 mm)) * 25-layers Magnetic Spectrometer – Too large and complicated, many cables dE measurement by SSD – dE/dx (1.5—3 GeV/c protons) < 14 keV/cm – dE/dx (1.0---1.5 GeV/c protons) = 16 keV/cm – dE/dx (electrons) = 16 keV/cm – Work for protons (p>1.5 GeV/c). – No. of signal cables?

19. Summary Being established the measurement of R AP below 1e-17. Promising results with 10-mm Al measurement. Improvement of factor 1/20 is expected with the current 10-cm Fe configuration. Fe/Scintillator Sandwich should be installed by Spring, and measure before the summer shutdown. Need to develop an advanced detector for the physics-data taking stage.