The double-sided silicon strip detector with excellent position, energy and time resolution Bachelorthesis by Eleonora Teresia Gregor

decay studies with active stopper Rare ISotope INvestigation at GSI (RISING) spectroscopy at relativistic energies scattering experiments with TOF measurement

Content Introduction and Motivation – RISING experiments The DSSSD as an active stopper in decay experiments –The detector model –The electronics –Testing the active stopper detectors –The RISING-setup The DSSSD as a timing detector in scattering experiments –The test experiment –Testing the thin detector model –Microchannel plate detectors –The electronics –Time resolution –Testing the MFA-32 Summary and Outlook

Radioactive ion beam production

The fragment separator FRS The FRagment Separator (FRS)

1 GeV/u U-238 beam 2.5g/cms Be target Experimental Setup 105 HPGe crystals (15 clusters) Efficiency: 9-14% Active Stopper DSSSD Array

γ β (ΔE signal) RISING Implantation-Decay Detector Heavy ion from FRS Decays after a certain time, according to half- life Emission of β-particle and prompt γ -rays Correlation via position (x,y) of ion hit and β- particle Animation: Berta Rubio

The double-sided silicon strip detector DSSSD by Micron Semiconductor Ltd *3mm 2 pixels; active area of 5*5 cm 2 W1(DS)-1000: –Thickness: 1000 µm –Depletion voltage: V W1(DS)-40: –Thickness: 40 µm –Depletion voltage: 10 V Schematic drawing provided by Micron Semiconductor Ltd.

Strip detectors M. Krammer: "Detektoren in der Hochenergiephysik"

The electronics for the active stopper Micron Semiconductor CAEN Nº Pixels: 256 Element Length: 49.5 mm Element width: 3.0 mm Active Area: 50x50 mm 2 Thickness: 40 & 1000 µm MPR-32 Charge Sensitive Preamplifier 32 channels Sensitivity switch, factor 5 Bias voltage up to ±400V STM channel NIM module shaper amplifier timing filter amplifier leading edge discriminator MRC-1 Remote controller via R-232 MHV-4 High precision bias supply 4 channels Current warning Voltage up to ± 400V ADC V785AF 32 channels 207 Bi energy spectrum All pictures from datasheets provided by mesytec/CAEN

The electronics for the active stopper

Testing with a 207 Bi-source K-conversion: 482 keV L/M-conversion: keV 570 keV K-conversion: 976 keV L/M-conversion: keV 1064 keV Transition Energies in 207 Pb: ΔE=1.6% ΔE=3.1%

Testing with a 207 Bi-source Analysis Programme: Go4 Shaping time: 1 µ s or 2.5 µ s FWHM Long shaping time improved energy resolution by ~ % Setting thresholds just above the noise level Gain factor: 12.2 Mean energy resolutions: –15-19keV for front junction sides –18-21keV for rear ohmic sides From: NIM A598 (2009), 754

Position resolution of a DSSSD Hit in a single strip -> position resolution of 3mm Hit in two or more strips -> centroid of the energy distribution -> position resolution better than 3mm All from: NIM A598 (2009), 754 Strip multiplicity for front (left) and rear (right) side Multiplicity distribution over strip number relative to the center hit

The RISING-setup 6 detectors in two rows of three Active stopper vessel: 2 mm Pertinax covered with 20 µ m pocalon carbon foil, measurement in dry nitrogen Problem: measure both electrons (energy <1 MeV) and implanted particles (energy ≥ 1 GeV) MPR-32 logarithmic pre- amplifiers: linear range of 2.5 or 10 MeV (70% of total range) and logarithmic range until 3 GeV S361: Shape evolution near 106 Zr S337: Structure of 132 In populated in the β-decay of 132 Cd: the ν f 7/2 π g 9/2 -1 multiplet on the doubly magic 132 Sn core. S350: Moving along Z=82, beyond the doubly- magic 208 Pb nucleus

S361: Shape evolution near 106 Zr GSI GPAC - March 2008 Study 104,106 Zr and neighbouring region projectile fission of 238 U 3.33 prolate sym. rotor 2.90 X(5) 2.0 spherical vibrator

GSI GPAC - March Cd production in projectile fission of 238 U followed by β-decay to 132 In S337: Structure of 132 In populated in the β-decay of 132 Cd: the νf 7/2 πg 9/2 -1 multiplet on the doubly magic 132 Sn core. The basic   structure information required for the shell model calculations.

GSI GPAC - March ,214,216 Pb production in projectile fragmentation of 238 U S350: Moving along Z=82, beyond the doubly-magic 208 Pb nucleus N/Z~1.0–1.6 ~3.0

Scattering experiments DSSSD Energy loss ΔE DSSSD Energy loss ΔE x, y Beam from FRS A, Z E~100MeV/u Target Be/Au CsI-detector Residual Energy E res Plastic scintillator t Start Plastic scintillator t Stop Germanium Cluster Detectors Fragmentation or Coulomb-excitation Particle has to be identified again Energy loss ~ Z 2 Total energy (E res +ΔE) and speed yield mass Time-of-flight measurement Scattering angle (twice position) Goal: Reduce number of detectors

Scattering experiments DSSSD Energy loss ΔE DSSSD Energy loss ΔE x, y Beam from FRS A, Z E~100MeV/u Target Be/Au CsI-detector Residual Energy E res t Start Plastic scintillator t Stop Germanium Cluster Detectors Fragmentation or Coulomb-excitation Particle has to be identified again Energy loss ~ Z 2 Total energy (E res +ΔE) and speed yield mass Time-of-flight measurement Scattering angle (twice position) Goal: Reduce number of detectors

Overview of the UNILAC-Experiment's Setup

Testing with a mixed α-source Energy resolution and calibration of the thin detector used for time measurement Mixed α-source: 239 Pu, 241 Am, 244 Cm Am-Peak used to determine energy resolution No data from badly damaged strip Y1 Pu MeV Am MeV Cm MeV ΔE=0.61%

The microchannel plate detector Entrance window (mylar foil); electrostatic mirror; position sensitive microchannel plate A particle passing the foil causes electrons to be emitted from it; which are diverted by the wire grid's electric field An entering electron hits the channel wall and creates additional electrons High voltages (2400 & 2500V) to attract the electrons Output signals have a low time jitter, but large random noise Н. А. Кондратев

The electronics for the UNILAC-Experiment

Calculating the time resolution Time resolution of two detectors adds as following: For a single detector: In case of two MCPs, the performance should be the same: The error is calculated through standard error propagation: The weighted mean is given as:

Time resolution with two microchannel plate detectors Using data collected over the whole MCP: Reasons not to do this: –burn-like spots –different flight paths Therefore: Time resolution with gates on single pixels of DSSSD Weighted mean of 35 pixels: Time difference between both MCPs, gate on time-7, energy-8 Time difference between MCPs

Test with a new preamplifier and matching discriminator built by Wolfgang König Cross talk between neighbouring strips is eliminated by an energy condition Energy strips covered Multiple peaks in spectra over entire strip – charge carriers need time to migrate to the electrodes Time resolution with the silicon detector Energy Strip 0& &7 4&5 Difference between MCP1 and DSSSD for time strip 7Signal from time strip 8 (dark blue) and 7 (light blue) Signal from channel 2 (dark blue) and 3 (light blue)

Time resolution with the silicon detector Data analysed pixel by pixel Two time resolutions per strip (MCP1 – Si & MCP2 – Si) Weighted mean of both: Time resolutions vary between 26 and 186 ps Mean of all pixels: Time difference between MCP 1 and DSSSD, gate on time-7, energy-2

Testing Mesytec's MFA channel fast amplifier optimised for high energy deposition: 100MeV to 2GeV Requires positive inputs 8 fast outputs, each the sum of four neighbouring channels negative output position internally coded In- and outputsides of MFA-32, from datasheet provided by Mesytec

Testing Mesytec's MFA-32 First test with 5.4MeV α-particles from 241 Am Second test at X7 with 48 Ca at 5.9MeV/u Energy signal (yellow) and time signal (light blue) from α-particles Energy signal (dark blue) and time signal (light blue) from 48 Ca-ions

Summary and Outlook Position resolution: 3mm or better Energy resolution: 1.8% for 1 MeV electrons and 0.6% for 5 MeV α -particles Time resolution: Mean of 54ps with large variation A future test will most likely reduce the number of detectors close to the target to one DSSSD for position, energy and time measurement

Sources H.Geissel et al., Nucl. Instrum. and Meth. B70 (1992) J. Simpson, Z. Phys. A358 (1997), 139 S. Pietri et al., Nucl. Instrum. and Meth. B261 (2007), 1079 H. J. Wollersheim et. al., Nucl. Instrum. and Meth. A537 (2005), 637 Zs. Podolyák et. al., Nucl. Instrum. and Meth. B266 (2008), R. Kumar et al., Nucl. Instrum. and Meth. A598 (2009), 754 D. Rudolph et al., Technical Report, V1.2, June 2008 Knoll, Glenn F.: Radiation Detection and Measurement; John Wiley & Sons, Inc. Micron Semiconductor Ltd. Mesytec CAEN GSI Analysis System Go4 Cern Data Analysis Framework ROOT A. E. Antropov et. al, Nucl. Phys. Proc. Suppl. 78: , 1999