Development of Diamond Detector at CNS 2011/Jan./12 Shin’ichiro Michimasa (CNS)

Contents Motivation  Physics attacked by using diamond detectors  Basic property of diamond material Producing of diamond detectors by CNS-MSU collaboration Fundamental test of diamond detectors  Operation of Diamond detector  Comparison of preamplifiers Next step of development Summary

Spectrometers at RIBF RIBF will be equipped with 3 spectrometers: ZeroDegree spectrometer (Kubo, RIKEN) multi-purpose completed in 2007 SAMURAI spectrometer (Kobayashi, Tohoku Univ.) large acceptance, multi-particle will complete in 2011 SHARAQ spectrometer (Univ. of Tokyo) high resolution, rotatable completed in 2008

SHARAQ spectrometer SHARAQ = Spectroscopy with High-resolution Analyzer of RadioActive Quamtum beams  BigRIPS × High-resolution Beamline × SHARAQ spectrometer BigRIPS provides High intense RI beam High-Resolution beamline realizes dispersion-matching transport against large momentum spread of RI Beam SHARAQ spectrometer analyzes momentum of reaction products with high resolution Diamond is a key detector for obtaining high-intense tracking and high timing resolution.

Physics Motivation Physical Programs with SHARAQ and Diamond detectors (DD) 1. Mass measurement by combining TOF and Brho. ⇒ High-timing resolution to achieve TOF 2. (p,n) measurement in inverse kinematics. ⇒ Timing-start counter installed near the 2nd target to measure neutron energy 3. Tracking detector for intense beam over 1MHz Our DD was designed as a timing detector Goal : Time resolution ~ 10 ps

Why Diamond ? Outstanding properties of Diamond  Extreme mechanical hardness and extreme high thermal conductivity  Broad optical transparency in region from IR to UV Insensitive for visible light  Diamond is a semiconductor (band gap = 5.47eV) and very high resistivity at room temperature (10 16  cm) No cooling and No p-n junction ⇒ Easy operation  High charge carrier mobility (e: 2200/h: 1600 cm 2 /Vs) Fast rise time of detector signal  High energy needed to remove carbon atom from the lattice (80 eV) Radiation hardness

Why Diamond ? Diamonds materials we can use  Single-crystal CVD diamond plate Maximum size: 5×5 mm 2, d=50,100,200,300  m (commercially)  Polycrystalline CVD diamond plate Maximum size: 50×50 mm 2, d=50,100,200,300  m (commercially) Development of large size of Polycrystalline CVD DD  Beam spot size : ~ 10×30 mm 2 at the F3 achromatic focus  Energy loss in the detector is large for heavy ions: ⇒ dE/dx ~ 100 keV/  m ~ 10 5 e-h/  m ( 12 N 250A MeV) obtain the number of e-h pair to overcome the S/N ratio.

Development of Diamond detector  2010/Apr.  Start the operation studies of diamond detector by using 10×10 mm 2 DD (DD of early stage, given by Munich)  Test of Preamp and pulse processing  Start the CNS-MSU collaboration  Producing of large size of DD 2 plates of CVD diamond detector (30×30×0.2 mm 3 ) 2010/Apr.-Jul.  Discussions the electrode design with MSU  Test of Munich DD by using an alpha source ( 241 Am) 2010/Oct.  12 N beam bombarded a 10mm-square DD 2010/Nov.-2010/Dec.  Evaporation of electrodes on 30mm-squre diamonds  Signal check of DDs at MSU 2011/11/Jan.  A diamond detector was delivered from MSU.

Diamond detectors Diamond detector of 10×10 mm 2 Diamond detector of 30×30 mm 2 This is used for studies of basic DD operations by using Alpha source and RI beams Arrived at CNS yesterday

Producing of large-size DD by collaboration with CNS and MSU CNS prepared pCVD diamond plates MSU made electrodes on diamond. Design are discussed together

Diamond materials for Detector Data sheet of Diamond material Uniformity of thickness is controlled precisely

Design for higher timing-resolution DD Design goal of DD timing resolution : 10 ps  Need to timing correction by hit-positions. Speed of signals on electrode : ~1.6 mm / 10 ps Face A (timing information)Face B (HV suppied)

Operation study by using small DD We study the properties of a DD.  Signal shape of DD  Charge collection depth  Long-time stability Basic experience to operate large-size DD.

Diamond signals by 5.4-MeV alpha  +HV Osc. 1GHz - Condition of DD 10mm-square DD HV: +500 V PreAmp: DBA-IV (G ~ 50dB) Noise level: ~ 20 mV (p-p) Signal: ~ 90 mV We can obtain signals from both side of Diamond detectors

Diamond signals by 5.4-MeV alpha Typical signal shape (DBA-IV) Rise time ~500 ps Pulse width ~1.9 ns (FWHM)

Osc. 500MHz Diamond signals by 180A MeV 12 N Setup Beam PL DD Diamond (PreAmp out) Plastic - Condition of DD 10mm-square DD HV: 360 V PreAmp: DBA-IV (G ~ 50dB) Noise level: ~ 10 mV (p-p) Signal: ~ 30 mV HV DD Beam Vacuum

Property of 10 mm-square DD Diamond (PreAmp out) Charge collection depth Q = 2.6 pC Based on - preamp gain (50dB) - num. of e-h by energy loss (13 eV/e-h pair) = How thick can electrons (holes) be collected Estimated Charge Collection Depth is ~ 10 micron. (~5% of generated e-h pairs.) CCD of First-stage pCVD diamond detectors is reported to be 12 micron. Recent pCVD DDs are improved and reported to be ~200 micron. We are expecting this value for large-size DD.

Signal rate of DD by an alpha source. Leak current of DD I ~ 100 nA 10mm-square DD + Preamp CVIDEC Noise level < 10 mV / Typical pulse height ~30 mV Thre -9.2mV At 600V, count rate seems not to be saturated. Due to small CCD, electric field is not enough to collect all charges in diamond.

Stability in long-time operation 10mm-square DD + Preamp CVIDEC HV = -300 V, Noise level < 10 mV Thre -9.2mV After set HV=0 Long time operation decreases pulse height of signals. After HV off, count rate was almost recovered.

Preamplifiers for optimized to DD Requirement for Preamplifier  Broadband amplification (up to ~ 2GHz)  High gain (>40dB) and good S/N ratio because of small charge signals. Preamplifiers for DD in commercial  DBA-IV (DBA series, developed at GSI)  CIVIDEC Broadband preamplifier  High frequency preamplifier by Fuji diamond Co.Ltd. (developed by KEK)  Broadband preamplifier by Iwatsu

Comparisons of Preamplifiers AC CIVIDEC DBA-IV Fuji-Diamond Iwatsu -600~+100V HV Coupling 40dB Non-invert dB (controllable) Non-invert Bandwidth 3M-2GHz 1M-2GHz 100k-1.8GHz 46dB Gain Input/Output Impedance. 50/50  Noise Level (p-p) 55dB 10k-2.5GHz -2.5k~+2.5kV AC ? 5 mV 30 mV 20 mV

Next step of development Beam time for 30mm-square DD  2011/Jan./22-24 ( 48 hours )  8.8A MeV Alpha beam at E7B beam line.  Points should be checked Charge collection depth Timing resolution Detection efficiency (coincidence with plastic scinti.) as a function of HV Charge information of signals Intensity dependence (Long-time stability)

DD developing beam time Detector setup and electronics

Summary Study of basic operation of pCVD diamond detector.  Check point for pCVD DD Charge collection depth. Pulse decreasing effect in long-time operation. Manufacturing of large DD by CNS-MSU collaboration  Size: 30×30×0.2 mm 3  Design for achieve good time resolution.  One detector delivered,  Beam study will be performed next weekend. Diamond detector will be installed for experiments in FY2011.

Collaborators S.Michimasa, M.Takaki, K.Kisamori, H.Miya, S.Go, S.Ota, E.Ideguchi, T.Uesaka, S.Shimoura (CNS) for SHARAQ collaboration A.Stolz, R.Zegers, M.Sasano (NSCL/MSU) Thank you for your attention