CJ Barton Department of Physics INTAG Meeting – GSI – May 2007 Large Acceptance Bragg Detector...

CJ Barton Department of Physics

INTAG Meeting – GSI – May 2007INTAG Meeting – GSI – May 2007

Large AcceptanceBragg Detector

atISOLDE


IntroductionIntroduction

• Background• Detector Ideas• Simulations and Design

ISOLDEISOLDElarge beam species availability and increased beam energieslarge beam species availability and increased beam energies

will continue to open exciting research opportunitieswill continue to open exciting research opportunitiesin nuclear physics in nuclear physics


Sample Reaction – Multiple Coulomb ExcitationSample Reaction – Multiple Coulomb Excitation

1.3 MeVEfficiency: 19% Resolution: 7 keV

at 0.045 v/c

Angular Range 150 - 530

= 20

= 3.50

Miniball Compact Disc Array

Particle Energy Detection and Position ResolutionNot always sufficient (Kinematics & Isobaric contamination)


Ion Chamber IdeaIon Chamber Idea

Segmented Ion Chamber• Z identification (Target/Beam/Isobaric Contamination)

• 00 hole for beam suppression/count rate and flux integration• /2 for detection of target and scattered beam

• Large acceptance for efficiency•Position-sensitive (angular distribution measurement and some Doppler correction)

• Allows for particle array(for stable target nuclei) near 900

• Allows for high-efficiency -ray array around target


Idea – Annular PPAC+Ion ChamberIdea – Annular PPAC+Ion Chamber

Segmented AnodeFront View

Segmented Anode

Side View

PPAC2o resolution

1mm

Frish Grid

X

XRadialField

Challenge – segmentation for good E/EConclusion – do not pursue

100

110

120

130

140

150

160

170

180

100 150 200 250 300 350 400 450

Te

I

E (

MeV

)

E (MeV)

Te 40deg

Te 10deg

I 10deg

I 40deg

E/E Plot Z ~ 50


Other Ideas: Gas-Silicon HybridOther Ideas: Gas-Silicon Hybrid

Gas

E

Gas-Silicon Hybrid

PositionSensitive

SiChallenge – 1/20 Z resolution

(parallel capacitance)

Most effective withE having about 50%Eloss

Challenge – Z resolutionConclusion – do not pursue

FrontView

SideView


Other Ideas: PPAC and BraggOther Ideas: PPAC and Bragg

Range in Bragg (50 mbar isobutane)12.1 +/- 0.2 cm

Radial Extent Angle Straggling 0.22 +/- 0.12 cm 0.34 +/- 0.15 degrees

0.0E+00

2.0E-02

4.0E-02

6.0E-02

8.0E-02

1.0E-01

1.2E-01

1.4E-01

1.6E-01

1.8E-01

2.0E-01

2.5E+09 3.0E+09 3.5E+09 4.0E+09 4.5E+09 5.0E+09

Distance from Target (Angstroms)Io

nis

atio

n (

ev/A

ng

stro

m)

As

Se

Cl

Side View

PPAC2o resolution

1mm

X

Frish Grid

X

Front View


Bragg DesignBragg Design

Inner Tubefield

shaping rings

FieldGradient!

ElectronTrajectories

Anode Segmentation and non-normal trajectories


Bragg Design – normal MINIBALL configurationBragg Design – normal MINIBALL configuration

Vacuum Hole10 degrees front3 degrees back

Challenges:Background


Bragg Design – altered MINIBALL configurationBragg Design – altered MINIBALL configuration

Bragg

Challenges:MINIBALL position

Anode Segmentation

Drift ofCharge

AndAnode

Segmentation

E Field

Z – resolution ~ 1/20 !


Bragg Design – Normal orientationBragg Design – Normal orientation

Too Simple – Too Hard to Construct

15o

55o

35o

Side View (Slice) TargetChamber

FlaredWith

RadialField


Thick Target Simulation: Thick Target Simulation: 7070SeSeBeam Spot (5mm diameter) + StragglingBeam Spot (5mm diameter) + Straggling

Front

Beam Axis

Back

30o202 MeV70Se, 70As

25 cm

Beam Spot Angle: 30.0 +/- 0.4 deg

Thick Target Energy 169 MeV (front) 146 MeV (middle) 128 MeV (end)

2 mg/cm2

104Pd

2.88 MeV/1x104 / sec

Range Straggle +/- 2.26 cm

Radial Straggle+/- 0.8 cm

Angle Straggling2.4 +/- 0.2 degrees


Thick Target Simulation: Thick Target Simulation: 7070SeSe

0

10000

20000

30000

40000

50000

15 20 25 30 35 40 45 50

Angle (5 degree bins)

Cro

ss s

ecti

on

(m

b)

0

0.5

1

1.5

2

2.5

3

Co

un

t R

ate

(io

ns/

sec)

Rutherford Calculation(projectile and scattered target)

overlap

CoulEx Calculation

CoulEx (mb) Rutherford (mb)projectile 404 67313

target 374 5996yield 0.05 /sec 5 /sec


132132Te CoulEx Experiment with BraggTe CoulEx Experiment with Bragg

BeamAxis

1 mg/cm2

48Ti

132Te, 132Sb

1x106 / sec

3.1 MeV/

Range in Bragg 12.3 +/- 1.0 cm

Radial Extent Angle Straggling 0.8 +/- 0.6 cm 1.2 +/- 0.9 degrees

Projectile and Target Energiesversus Laboratory Angle (deg)

0

50

100

150

200

250

300

350

400

450

0 50 100

Laboratory Angle (deg)

En

erg

y (

Me

V)

Projectile

Target

0.00E+00

5.00E-02

1.00E-01

1.50E-01

2.00E-01

2.50E-01

3.00E-01

2.5E+09 3.0E+09 3.5E+09 4.0E+09

Distance from Target (Angstroms)

Ion

isat

ion

(ev

/An

gst

ron

)

Te

Ti

Sb


Calculations: Calculations: 132132TeTe

Rutherford Calculation(projectile and scattered target)

CoulEx Calculation

CoulEx (mb) Rutherford (mb)projectile 292 5819

target 226 3484yield 2.1 /sec 42 /sec

0500

10001500200025003000350040004500

15 20 25 30 35 40 45 50

Angle (5 degree bins)

Cro

ss s

ecti

on

(m

b)

0

10

20

30

40

50

60

Co

un

t R

ate

(io

ns/

sec)

overlap


LimitationsLimitations

Electron Drift Radial Straggle ~ 1mm

Electron Drift Time to Peak ~ 1sec (Field Gradient)

Rutherford Scattering – Physical Barrier (per experiment)for space charge

Anode Pad Segmentation Efficiency and Isolation


Current Design (geant4)Current Design (geant4)

540

500

300

100

60

57.8

8 cm

22.2

6 cm

25 cm

2.0 cm100

SegmentedAnodePlates

Beam Line Guide

Element 110o-30o

Note Gap

Element 230o-50o


Current Design (geant4)Current Design (geant4)

Note Gap


Solid Angle of DetectorSolid Angle of Detector


Map of 1 Segment - GarfieldMap of 1 Segment - Garfield

Electric FieldGradient ~ 100 V/cm

Cathode-Grid~ 28 cm

Grid-Anode~ 2 cm

SegmentedAnode

Frisch Grid

GroundedOuter

Surface

Labels


Voltage Contour Map of 1 SegmentVoltage Contour Map of 1 Segment

Note gap


Ion Track and IonizationIon Track and Ionization

SegmentedAnode


Ionization Profile and SignalIonization Profile and Signal

SRIMIonization

profile

GarfieldChargeDensity

Garfield – induced signalCurrent versus Time

Z


Signal Distribution on PadSignal Distribution on Pad

Whole Signal Arrival Time Electron Offset ~ 1mm


Technical DrawingTechnical Drawing

Largerat 53o

and 6o

ModifiedRing supports





6 IdenticalSegments

2 Elements ineach Segment



4 segmentedAnode PadsPer Element

48 AnodeChannels






PlansPlans

Finish Design of Bragg Volume (gas flow + support)

PPAC Design + target chamber + transit line

Construct and Test 1 segment (2 elements)

Improve Garfield simulation of detector

Incorporate into Miniball Geant4 simulation (efficiency)


PeoplePeople

University of YorkCJ Barton, JE Butterworth, D Bandyapadhyay, P Joshi, P Mumby-Croft, PE Kent

Manchester UniversityJF Smith, BJ Varley

STFC DaresburyM Labiche, R Griffiths, J Strachan

CERN/ALICER Veenhof

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CJ Barton Department of Physics INTAG Meeting – GSI – May 2007 Large Acceptance Bragg Detector...

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