1 / 12

Studies on High QE PMT

Studies on High QE PMT. Tadashi Nomura (Kyoto U.) Contents Motivation Performance of H7422P-40 Application to Scintillation counter with WLSF readout Summary. K  pnn experiment needs hermetic veto system. Major K L decay modes K L  p + p - p 0 (13%) K L  p e n(g) (39%)

mea
Download Presentation

Studies on High QE PMT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Studies on High QE PMT Tadashi Nomura (Kyoto U.) Contents • Motivation • Performance of H7422P-40 • Application to Scintillation counter with WLSF readout • Summary Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  2. Kpnn experiment needshermetic veto system Major KL decay modes KLp+p-p0 (13%) KLpen(g) (39%) These may fake the signalif charged particles are missed Cause of inefficiency p-pp0n (all neutrals and lost) e+ annihilated with materials Detection before these interactions (i.e. with low energy deposition)reduces the inefficiency Motivation Signature = 2g + nothing Veto detectors surrounding Decay Region Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  3. Simple Consideration of Inefficiency In case of loss due to p-pp0n reaction • Cross section s(CH),max ~100mb (at the resonance peak: Ep~170MeV) • Required inefficiency < 10-4 • Energy deposit ~ 2MeV/cm • Edeposit before Pint=10-4 ~ 40keV 6x1023[n/mol] / 104[g/mol] x 8[CH pair/n] x 1[g/cm3] x 100x10-27[cm2] x (thickness) = 10-4 thickness ~ 200mm, Energy deposit ~ 40keV (Note: Resultant p0 can be detected by photon veto detectors and thus inefficiency might be smaller) How many photoelectrons per 40keV can we obtain? High Quantum Efficiency (QE) PMT desired Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  4. Example: KOPIO Downstream CPV • Beam pipe liner inside pre-radiator / calorimeter • Counter should be inside vacuum, but it’s desirable to locate PMT outside  Long WaveLength-Shifting-Fiber (WLSF)  Small light yield  Need High QE PMT Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  5. H7422P-40 QE=30-40% for Green High QE PMT : Hamamatsu H7422 • GaAsP photocathode • Sensitive area: 5mm in diameter • Metal channel dynode structure • Price ~1.8k$ Measured QE using LEDs(relative to bi-alkali PMT) Expected QE GaAsP (H7422) Calculated fromrelative QE andbi-alkali catalog value Bi-alkali (H7415) Peak Wavelength of WLSF Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  6. Stable upto 1MHz gain drops above 200kHz Basic Properties of H7422 Light yield: 100p.e. Rate dependence Linearity Gain~6x106 Sensitivity map Light yield: 1000p.e. Gain~106 Linearity not so good(even within 100 p.e.) Structure due to focusing mesh was seen… (~10% dip) Improvement might be possible by optimizing base circuit Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  7. High QE PMT + Scintillator + WLSF • Test configuration • PMT: H7422P-40 • Scintillator: EJ-212 (ELJEN) 3mm-thick, 1m-long • WLSF: Y11(200) (Kuraray) 1mm-diameter • Machined groove, 1cm-pitch, bundle 7 fibers • Wrapped by Aluminized mylar 90Sr (Edep~580keV) 70 p.e. / 0.58 MeV 120 p.e. / MeV Results: 70 p.e (both) with High QE PMT (x 3~3.5 larger than with Bi-alkali PMT) Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  8. WLSF attenuation • Attenuation in WLSF alone • with LED-excited, viewed by High QE PMT • lL=6.1m • AL/AS ratio decreases if measured by bi-alkali PMT(longer wavelength ~ longer attenuation) • Attenuation in Scinti + WLSF • Consistent well with WLSF alone • In case of 4m long WLSF(1m in Scinti + 3m outside vacuum),Light yield will be 46% of our test result 120 x 0.46 x 40x10-3 = 2.2 p.e. / 40keV AS=9.0 , lS=1.0m AL=12.9 , lL=6.1m Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  9. Further Effort to Increase Light Yield • Use thicker WLS fiber • Better acceptance of primary scintillation lights • 1.0mm  1.5mm diameter • 30% increase expected (by our measurement) • Use clear fiber to transport light • Longer attenuation • 1m WLSF in Scintillator + 3m clear fiber (outside vacuum) • 50% improvement expected Connection ~90% x attenuation ~75%  68% cf. 46% attenuation for WLSF Need large area PMT cathode to read a bundle of 7 fibers 5mm  8mm diameter Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  10. Summary (1) • High Quantum Efficiency PMT Hamamatsu H7422P-40 (GaAsP photocathode) • Basic properties • QE : 30-40% for green light ~3 times larger than bi-alkali PMT • Linearity : not so good if we use “default” base circuit • Rate capability : stable upto 1MHz for 100 p.e. light • Application to Scintillator + WLSF • 120 p.e. / MeV (sum of both end) with 1m-long test counter~3 times larger than bi-alkali PMT, as expected Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  11. Summary (2) • Application to KOPIO DS Charged Particle Veto • In case we use 4m long WLS fiber, 2.2 p.e. / 40keV (sum of both end) will be expected • Threshold of 3 p.e. in both end, for example (6 p.e. in total) inefficiency will be 3x10-4 (without help by “backup” photon vetoes) • Effort to increase light yield • 1mm  1.5mm diameter fiber ( x 1.3 expected ) • Use clear fiber to transport long distance • Change reflection material (Aluminized mylar  Al evaporation?) Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

  12. Further High QE PMT issues • Large sensitive area desired • In order to use thicker fibers • Need negotiation with the vendor (Hamamatsu) • Linearity might be improved • Not so good with “default” base circuit • Optimize base circuit • Life time of photocathode? • Degradation of GaAsP ? • Long-term test is planned Tadashi Nomura (Kyoto U), KRare05 at Frascati, Italy

More Related