active targets: from maya to actar tpc

Riccardo Raabe – Instituut voor Kern- en Stralingsfysica, K.U.Leuven, Belgium Sevilla – 7 & 8/11/2011

Active Targets:From Maya to ACTAR TPC

Riccardo RaabeInstituut voor Kern- en Stralingsfysica

K.U.Leuven

6th DITANET Topical Workshopon Particle Detection Techniques

Principle Maya ACTAR TPC Design Tests MM Electronics


Outline

The active target

Motivation and principlePresent devicesConfigurations: physics cases, dynamic ranges

Requirements for the new instruments

Goals and designTests with bulk micromegasElectronics



Motivation: reactions with the most exotic beams

Opportunities at the present and future RIBs facilities:SPIRAL2, FAIR, HIE-ISOLDE, RIKEN, FRIB, ISAC2...Use direct and resonant reactions as spectroscopic toolto study the evolution of nuclear structure far from stability



Instruments

“Usually” (RIBs):Target is a foilSolid-state detection arrays

Good resolutiononly if gamma-ray detectionlow luminosity

Most exotic (weakest) beams?

Maximizetarget thickness detection efficiency



The active target concept

Time-Projection Chamber (TPC)…

Electrons produced by ionizationdrift to an amplification zoneSignals collected on a segmented“pad” plane 2d-image of the track3rd dimension from the drift timeof the electrons

…+ the detection gas is the target

Large target thicknessand still good resolutionGood efficiency,low detection threshold



pBeam from FRS

Present devices: IKAR and CENBG TPC

IKAR NPA 712 (2002) 247

Hydrogen gas, 10 barMultiple ionization chambersHigh energy beamElastic scattering of halo nuclei

CENBG TPC NIMB 266 (2008) 4606

Mixture 90% Ar + 10% CH4, ≈1 bar

Amplification: GEMPad plane: micro-groove detector(orthogonal strips)2p-emission decay studies



Present devices: MayaMaya NIMA 573 (2007) 145

Various gases: C4H10, D2, 4He+2%CF4, from 30 mbar to 1 bar

Amplification: wires and inductionPad plane: hexagonsAdditional detectors for particlesescaping the gas volume

MayaPrinciple ACTAR TPC Design Tests MM Electronics


Maya results: identification of 7H

8He(12C,13N)7H → 3H+4n15.4 MeV/nucleon (SPIRAL)13N (10 MeV) stoppedin 1.3 mg/cm2 carbon

active target

Identification of channel:kinematic reconstruction3H in CsI detectors13N in gas volumeidentification (separate from 12C…)[“easy” because it is the highest Z]

M. Caamaño et al., PRL 99 (2007) 062502



Maya results: 11Li(p,t)9Li transfer reactionI. Tanihata et al., PRL 101 (2008) 192502

9Li tritons

C4H10 150 mbar (1.7 mg/cm2)

Both particles identified




C4H10 150 mbar (1.7 mg/cm2)

Both particles identified




C4H10 150 mbar (1.7 mg/cm2)

Both particles identifiedMeasure angles kinematic reconstruction



Maya results: mass of 11LiT. Roger et al., PRC 79 (2009) 031603(R)

C4H10 350 mbar9Li stopped in the detector, 3H in Si at 0 degreesMeasure path length



Maya results: Giant Monopole Resonance in 56Ni

Diamond

56Ni50 MeV/u d

Deuterium 1 barShield on beam path!Measure energy and angleof scattered d (at least 10 pads)

C. Monrozeau et al., PRL 100 (2008) 042501



Requirements with the new physics cases

Various physics cases require different configurations “adaptable” instrument Different facilities: transportableRobust(reproducibleresults, “stable” operation)

ACTAR TPC DesignMayaPrinciple Tests MM Electronics


Requirements with the new physics cases

Detect particles with(very) different charges:dynamic range 103

Increase spatial efficiencydetect multiple tracksImprove (keep) energy andposition resolutionImprove acceptable beam intensityand counting ratesIncrease gain

Work upon…Detector hardwareElectronicsData acquisition software



ConfigurationsACTAR TPC AIP Conf. Proc. 1165 (2009) 339

Cubic geometry (mainly)Amplification: Micromegas, GEMAncillary detectorsIndependent pads, 2x2 mm2

AT-TPC, TACTICCylindrical geometryMagnetic field to confine particles

≈250 mm

E



Advantages

Micro-Pattern Gaseous DetectorsUniformity, robustnessEnergy resolution?Flexibilityvary amplification gapcombine MM and GEMs…

Independent padsVary voltage on different areasMultiple tracks

Resonant reactionsInteraction pointRecoil E and angle

Beam

Recoil protonResonance

region



Advantages



Inelastic scatteringInteraction pointBeam countingDifferent configurations

Beam



Advantages



Transfer reactionsInteraction pointRecoil light particleenergy and angle

Beam

Solid-state telescopes

Light recoils



Prototype tests (bulk micromegas)

Angular resolutionHe+CF4 (2%)

Tests MM ACTAR TPC DesignMayaPrinciple Electronics




Resolution <1.3° FWHM





Resolution < 1.3° FWHMAcceptable for very short tracks too




Energy resolutionα particles in Ar+CF4(2%) 1100 mbar





Path length: > 0.8 mm





Path length: > 80 keV FWHMCharge: > 80 keV



General Electronics for TPCs – GET

High front-end density

High-rate throughput(selective readout,zero suppression)

High S/N ratio

High dynamic range

Manage time stamp,other detectors, control...

Intelligent triggerL0 externalL1 multiplicityL2 topology

ElectronicsTests MM ACTAR TPC DesignMayaPrinciple


GET: The AGET chipBased on the AFTER asicAmplification, detection and storagex64: CSA, shaper, discriminator, memory(sampling from 1 MHz to 100 MHz)Highly configurable



Dynamic range

PossibilitiesElectronics (better preamps)Software (different gains on pads)Hardware: mask the beam

TACTIC



Summary

Active targets are very promising instrumentsfor research with exotic beams

Large target thickness with no loss in resolutionLow thresholdsVersatile, different configurations possible

Many parameters to considergas, pressure, electric field, drift velocity, dynamic rangeThe new generation: ACTAR TPC

Improvements in dynamic range, track multiplicity, event rate…Configuration, amplification technologyElectronics and softwareTests and simulation work



Configurations (physics cases)

Beam

Recoil protonResonance

region

Resonant reactionsEnergy of the beam to reachthe resonance of interestPressure adjusted to stop the beamat the end of the gas volumeDetection of light recoilsscattered forward

Exotic nuclei DetectionActive targets

Resolution of interaction pointDynamic range

Measure: interaction pointidentification recoilE, angle recoil particle


Beam

Configurations (physics cases)

Elastic and inelastic scattering

High pressure for target thicknessand stopping of light recoil particles

Beam leaves the detection volume

Measure E and angle of light recoils

If projectile heavydynamic range has to be large


Energy (position) resolutionLow thresholds, dynamic range


Configurations (physics cases)Transfer reactions

(p,d), (d,p), (4He,t), (3He,d), (p,t)…Beam leaves the detection volumeLight recoil at all angles and energies!Pressure adjusted for the productsof interestIdentification light recoilMeasure E, angle of light recoil

(d,p): low energy protonsat backward anglesPopulation of unstable systems:multiple tracks

Beam

Solid-state telescopes

Light recoils



Measurements with exotic nuclei

Fragmented and post-accelerated RIBs reaction methods now available on exotic nuclei

Elastic and inelastic scatteringResonant reactionsDirect reactions

Close to driplines:Exotic decayswith ion emission

Charged-particle detection methods are central

Exotic nuclei Active targets Detection


Requirements on detection methods

Low-intensity beams efficiency is keyIdentification of channel particle IDResolution

Reactions: inverse kinematicsHeavy beam on a light target

beam beam-likemagneticspectrometer

light recoilcharge-particle array

Reconstruct kinematics from E and θ of emitted particles(two quantities are sufficient to identify the channnel)



Reactions: kinematicsExample: transfer reactions

“Universal” kinematic curves placement of detector depends on channel to be detected (Q-value)Kinematic compression resolution, low thresholds



Configurations

Resolution in E*Light beam:better detect beam-likeparticle (limit on angularresolution)

Heavier beam:better detect light recoil(limit on E resolutionfrom straggling in thetarget)

In general:much worse thandirect kinematics



T-REX

Instruments

Charged particle arrays:solid-state telescopes (Si, Si+CsI...)resolution vs. costHow to improve resolution-ray: very good resolutionbut low efficiency, no g.s.-to-g.s.



Present and future devicesACTAR AIP Conf. Proc. 1165 (2009) 339

Cubic geometry (mainly)Amplification: MicromegasE and T from pads (≈16000 channels)Larger dynamic range(Electronics, pad independence)Multiple tracks

AT-TPC, TACTICCylindrical geometryMagnetic field to confine particles

≈250 mm



Detector parameters

Gas and pressure mostlydictated by physics

Electric field: optimize forAmplificationDrift velocityof electrons

Drift velocity:spatial resolution is

δx = vdrift δt

vdrift ≈ 5 to 100 μm/ns δt ≈ 200 to 10 ns

NIM 159 (1979) 213



Dynamic range

External detectors are expensive contain particles in gas volumeHigher pressure stronger signal from light ions

butLimit imposedby Eloss of beam particle

3 orders of magnitude difference!

PossibilitiesElectronics (better preamps)Software (different gains on pads)Hardware: mask the beam



Measured quantities

EnergyCollected chargePath length (range)

AngleExternal detectorsTrack reconstruction



Track reconstruction T. Roger, PhD Thesis

Charge distributiondepends uponamplification technologyand pad shape

Wires GEM

Micromegas



Simulation of the charge collectionto test reconstruction algorithms

Hyperbolic Secant Squared1. search for maxima along axes2. find centroids3. fit straght line through centroids

Accuracy: 0 to 1 degreesdepending on orientation




Global Fitting methodFor small charges, not spread(light particles, high energies)

not ok for θ<10 deg




Energy from collected charge T. Roger, PhD Thesis

IKAR

From pulse analysis:Integral recoil energy TR (EFWHM 90 KeV)

Risetime recoil angle R (FWHM 0.6°)

Time difference anode-cathode vertex point ZV (zFWHM 110 m)



Energy from range: end point T. Roger, PhD Thesis

Charge profileBragg peak:threshold effects

Threshold at 5% Threshold at 10%

xend = (xlast + xlast–1)/2 + Δ(slope)

Charge fitaccuracy ≈1.5 mm



Energy from range: reaction vertex T. Roger, PhD Thesis

Large uncertaintiesfor short tracksand small anglesUse charge profile instead



Particle identification

Energy vs. range Curves and tables (ex. SRIM)Need accurate rangeand a good calibration of padsto extract the dE/dx information



Calibrations

EnergyInduction: charge in wires with pulserAlignment of pad gainsCalibrated (alpha) source

TimeCalibrate electronics, or“Physics” calibrationusing a known reaction



Summary

Active targets are very promising instrumentsfor research with exotic beams

Large target thickness with no loss in resolutionLow thresholdsVersatile, different configurations possible

Many parameters to considergas, pressure, electric field, drift velocity, dynamic rangeMeasurements

Track reconstruction: check algorithms against simulationEnergy: from collected charge or from range(→ track reconstruction, energy loss tables)Particle ID from Eloss: limited by spatial resolution and dE/dx on pads



ExercisesPressure to stop a beam (resonant)Which energy of beam in case of proton detection(resonant elastic)Which spatial resolution necessary to separate twokinds of particles.Given a kinematic plot, calculate acceptance and E resolutionfor various values of the pressure


Outline

Exploring exotic nucleiRequirementsTechniques

The active targetPrinciplePresent devicesConfigurations: physics cases, dynamic ranges

Particle detection and identificationAlgorithms for track reconstructionEnergy: charge and rangesParticle identificationCalibrations


active targets: from maya to actar tpc

Documents

detection gas

halo nucleicenbg tpc

hydrogen gas

gas volumeidentification

active targets

maya results

gempad plane

inductionpad plane