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May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy1 KOPIO Beam Catcher Tadashi Nomura (Kyoto U.) Contents –What is Beam Catcher? –Concept.

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Presentation on theme: "May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy1 KOPIO Beam Catcher Tadashi Nomura (Kyoto U.) Contents –What is Beam Catcher? –Concept."— Presentation transcript:

1 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy1 KOPIO Beam Catcher Tadashi Nomura (Kyoto U.) Contents –What is Beam Catcher? –Concept and Design –Expected Performance –Proof of Principle –Summary

2 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy2 Veto detectors surrounding Decay Region Particles can escape through the beam hole Task K   experiment needs hermetic veto system Charged particles –Can be swept out from the beam and detected outside Photons –Must be detected inside the beam  Need “in-beam” photon detector Beam Catcher Signature = 2  + nothing

3 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy3 Challenge “In-beam” environment High intense beam (necessary to observe >100 K   ; Br~10 -11 ) –A vast amount of neutrons (~30G/spill in KOPIO)  Produce protons, pions, (  and e + /e - ) in the detector –Most KLs survive after decay region (~300M/spill)  Decay into , ,e + /e - in the detector  These secondary particles fire the counter and disturb its primary function !! Spill length ~ 5 sec

4 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy4 Solution Utilize Cherenkov radiation Aerogel tile (n=1.05) or Acrylic slab radiator  Avoid detection of slow particles from neutron interactions Slow , p and other hadrons cannot emit lights. Use direction information Segment the detector into many modules and require coincidence along the beam direction  Catch forward photons only Reduce fake signal due to  from secondary  0 (neutron interaction and K L decay in the detector)

5 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy5 Aerogel Catcher in Beam Converter (Lead) + Radiator (Aerogel tile) Sensitive area of 30cm x 30cm Like “Sandwich” detector by modules’ array aerogel flat mirror Cerenkov light lead sheet 5inch PMT Module funnel  red: e + /e -, blue: photon Example of  event (MC) Plan view Coincidence

6 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy6 Guard Counter in Halo Region Converter (Lead) + Radiator (Acrylic slab) Sensitive area of 15cm x 15cm “Sandwich” detector Total reflection condition in light transportation can reduce neutron’s signal –e + /e - emit large angle Cherenkov lights  meet the total reflection condition –Slow particles cannot emit light or generate only small angle emission which escape to outside of the slab Photon Neutron

7 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy7 KOPIO Catcher System In-beam Aerogel Catcher Module size: 30cm x 30cm Pb converter: 2mm per layer Number of modules: 420 –12-21 in horizontal with beam divergence –25 layers along beam (8.3 X 0 in total) Z gap between layers: 35cm Halo Guard counter Just before Aerogel Catcher ( 2mm Pb + 10mm Acrylic ) x 8 layers x 3 modules Top view 12m downstream of main detector Beam envelope

8 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy8 Location of Catcher System Beam Catcher Decay Region

9 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy9 Expected Performance by MC (1) Aerogel Catcher EfficiencyY position dependence 99% @ 300MeV Beam core

10 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy10 Expected Performance by MC (2) Hit probability for Neutrons 0.3% @ 800MeV Hit probability for K L s Dominated by decays in the Catcher

11 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy11 Signal Loss due to Catcher False Hit Accidental hit due to neutrons may kill K   signal Total false hit probability was found ~ 0.4 events /  -bunch –Integrated over the duration consistent with the arrival time of  from our signal K L If we set the time window to be 3ns, signal loss due to false hit will be 4.6% –Calculation based on random effect –Detailed studies by MC under way Neutron rate False hit (rate x hit prob.) False hit rate due to neutron Apply timing cut…

12 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy12 Efficiency Loss due to Blindness Catcher may be “blinded” due to other activities  Blinded modules become less efficient for photons –Photon efficiency loss found to be 1.1% (prompt  + neutrons) –Double pulse resolution is quite important !! (We used 3ns in the calculation above) Hit pattern of prompt beam  Overlay on  event Expected event map This cluster survives This cluster be killed

13 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy13 Proof of Principle Prototype 1 (2001-2) –1/4 size, flat mirror light yield Prototype 2 (2002-3) –1/4 size, parabolic mirror light yield response to proton (as substitute for neutron)  Check single layer eff. / two-layers’ coincidence  Good agreement with MC (with gas scintillation) PT2 PT1

14 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy14 Summary (1) In-beam Photon Veto in KOPIO Beam Catcher System –Aerogel counter inside beam –Acrylic sandwich counter in halo region Expected performance meets our requirement –High efficiency for photons (>99% @ 300MeV) –Low fake hit probability due to neutrons (0.3% @ E kin =800MeV) –Signal loss due to false hit will be ~5% –Catcher efficiency loss due to blindness ~1%

15 May 26-27, 2005Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy15 Summary (2) Proof-of-Principle experiments have been done –two generations of prototype –MC is found reliable  We are ready for production !! Full size prototype now under construction


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