The double-sided silicon strip detector with The double-sided silicon strip detector with excellent position, energy and time resolutionexcellent position, energy and time resolution

Bachelorthesis by Eleonora Teresia Gregor

decay studies with active stopper

Rare ISotope INvestigation at GSI (RISING)Rare ISotope INvestigation at GSI (RISING)

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scattering experimentswith TOF measurement

ContentContent

• 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 productionRadioactive ion beam production

The fragment separatorThe fragment separator FRSFRS

The FRagment Separator (FRS)The FRagment Separator (FRS)

•1 GeV/u U-238 beam

•2.5g/cms Be target

Experimental SetupExperimental Setup

•105 HPGe crystals (15 clusters)

•Efficiency: 9-14%

•Active Stopper DSSSD Array

γ

β (ΔE signal)

RISING Implantation-Decay Detector 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 detectorThe double-sided silicon strip detector

• DSSSD by Micron Semiconductor Ltd.

• 256 3*3mm2 pixels; active area of 5*5 cm2

• W1(DS)-1000: – Thickness: 1000 µm– Depletion voltage: 180-200 V

• W1(DS)-40:– Thickness: 40 µm– Depletion voltage: 10 V

Schematic drawing provided by Micron Semiconductor Ltd.

Strip detectorsStrip detectors

M. Krammer: "Detektoren in der Hochenergiephysik"

The electronics for the active stopperThe electronics for the active stopper

Micron SemiconductorMicron Semiconductor

CAENCAEN

Nº Pixels: 256Element Length: 49.5 mmElement width: 3.0 mmActive Area: 50x50 mm2

Thickness: 40 & 1000 µm

MPR-32Charge Sensitive Preamplifier

32 channelsSensitivity switch, factor 5Bias voltage up to ±400V

STM-16

16 channel NIM module shaper amplifiertiming filter amplifier leading edge discriminator

MRC-1

Remote controller via R-232

MHV-4High precision bias supply

4 channelsCurrent warningVoltage up to ± 400V

ADC V785AF32 channels

207Bi energy spectrumAll pictures from datasheets provided by mesytec/CAEN

The electronics for the active stopperThe electronics for the active stopper

Testing with a Testing with a 207207Bi-sourceBi-source

K-conversion:

482 keV

L/M-conversion:

554-567 keV

570 keV

K-conversion:

976 keV

L/M-conversion:

1048-1061 keV

1064 keVTransition Energies in 207Pb:

ΔE=1.6%

ΔE=3.1%

Testing with a Testing with a 207207Bi-sourceBi-source

• Analysis Programme: Go4

• Shaping time: 1µs or 2.5µs FWHM

• Long shaping time improved energy resolution by ~0.1-0.2%

• 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 DSSSDPosition 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) sideMultiplicity distribution over strip number relative to the center hit

The RISING-setupThe RISING-setup

•6 detectors in two rows of three •Active stopper vessel: 2 mm Pertinax covered with 20 µm 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 106Zr

•S337: Structure of 132In populated in the β-decay of 132Cd: the νf7/2 πg9/2

-1 multiplet on the doubly magic 132Sn core.

•S350: Moving along Z=82, beyond the doubly-magic 208Pb nucleus

Scattering experimentsScattering experiments

DSSSD

Energy loss ΔE

DSSSD

Energy loss ΔEx, y x, y

Beam from FRS

A, Z

E~100MeV/u

Target

Be/Au

CsI-detector

Residual Energy

Eres

Plastic scintillator

tStart

Plastic scintillator

tStop

Germanium Cluster

Detectors

•Fragmentation or Coulomb-excitation

•Particle has to be identified again

•Energy loss ~ Z2

•Total energy (Eres+ΔE) and speed yield mass

•Time-of-flight measurement

•Scattering angle (twice position)

•Goal: Reduce number of detectors

Scattering experimentsScattering experiments

DSSSD

Energy loss ΔE

DSSSD

Energy loss ΔEx, y x, y

Beam from FRS

A, Z

E~100MeV/u

Target

Be/Au

CsI-detector

Residual Energy

Eres

tStart

Plastic scintillator

tStop

Germanium Cluster

Detectors

•Fragmentation or Coulomb-excitation

•Particle has to be identified again

•Energy loss ~ Z2

•Total energy (Eres+ΔE) and speed yield mass

•Time-of-flight measurement

•Scattering angle (twice position)

•Goal: Reduce number of detectors

Overview of the UNILAC-Experiment's SetupOverview of the UNILAC-Experiment's Setup

Testing with a mixed Testing with a mixed αα-source-source

• Energy resolution and calibration of the thin detector used for time measurement

• Mixed α-source: 239Pu, 241Am, 244Cm

• Am-Peak used to determine energy resolution

• No data from badly damaged strip Y1Pu-239

5.245 MeV Am-2415.476 MeV

Cm-2445.902 MeV

ΔE=0.61%

The microchannel plate detectorThe 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-ExperimentThe electronics for the UNILAC-Experiment

Time resolution with two microchannel plate detectorsTime 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:

pstotMCP 11144

2

ps0.48.75

Time difference between both MCPs, gate on time-7, energy-8Time 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 12-15 covered

•Multiple peaks in spectra over entire strip – charge carriers need time to migrate to the electrodes

Time resolution with the silicon detectorTime resolution with the silicon detector

Energy

Strip 0&1

8

9

10

11

2

3

6&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 detectorTime 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:

ps3454

22

21

22

221

1

11

11

Time difference between MCP 1 and DSSSD, gate on time-7, energy-2

Testing Mesytec's MFA-32Testing Mesytec's MFA-32

•32 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-32Testing Mesytec's MFA-32

• First test with 5.4MeV α-particles from 241Am

• Second test at X7 with 48Ca at 5.9MeV/u

Energy signal (yellow) and time signal (light blue) from α-particlesEnergy signal (dark blue) and time signal (light blue) from 48Ca-ions

Summary and OutlookSummary 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

SourcesSources

• 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), 4589-4594• 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. http://www.micronsemiconductor.co.uk• Mesytec http://www.mesytec.com• CAEN http://www.caen.it/• GSI Analysis System Go4 http://www-win.gsi.de/go4/• Cern Data Analysis Framework ROOT http://root.cern.ch/• A. E. Antropov et. al, Nucl. Phys. Proc. Suppl. 78:416-421, 1999