GSEM project SPENVIS/GEANT4 Workshop, Leuven, Belgium, 3 - 7 October 2005 Daniel Haas, DPNC Genève Outline Description of GSEM HEP Range Telescope Radiation

GSEM projectSPENVIS/GEANT4 Workshop,

Leuven, Belgium, 3 - 7 October 2005Daniel Haas, DPNC Genève

Outline Description of GSEM HEP Range Telescope Radiation in Space GEANT4 Simulation Outlook & Conclusions

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 2

The GSEM project… General Space Environment Monitor:

Multi-Purpose Detector to monitor critical environmental data, like: Radiation (High Energy Particle Sensor) Vibration Debris Plasma/Discharge


…The GSEM project… ESA/ESTEC contract 10619/04 Collaborators:

Contraves Space, Zürich (SREM) Vibrometer, Fribourg DPNC, Université de Genève

• Prof. Martin Pohl, Prof. Divic Rapin, Dr. Daniel Haas, Denis Rosset

Phase A finished Phase B ongoing


…The GSEM project Key Issues:

Very light: Central Unit and HEP sensor ~ 1 kg

Low Power:Central Unit and HEP sensor ~ 1 Watt

Modular:Easy integration of other sensor systems


The HEP Sensor System……what was existing

Jan 2005: ESA Workshop on Ionizing Particle Measurements in Space: Future Technology Priorities:

• High fidelity energetic particle telescopes (EPT…)• Sub-kg general particle spectral monitors (GSEM)

incl. miniaturized dose rate monitors Problems of existing Monitors:

• Poor separation of electrons, protons and ions• Measurement of deposited energy only Difficulties in data interpretations


The HEP Sensor System……what do we need

HEP sensor system of GSEM should provide: e/p separation of 1 in 10-3

Measure incoming particle energy with good fidelity and multiple bins

Data needs to be corrected for dead time, channel and particle cross-feed

Simplified data interpretation


The HEP Sensor System……Revised Design Requirements by ESA

Distinguish electron/proton/ion Measure incoming particle energy

Measure E and dE/dx Energy ranges:

Electrons: 120 keV - 7 MeV Protons: 3 MeV - 300 MeV Ions: 1 - 70 MeV/cm2/mg

Viewing angle at least 20o

Sampling rate: 500 kEvents/s with dead time correction


The HEP Sensor System……Design Approach

Range Telescope with: Measured quantities:

• Range• dE/dx in all layers

Stack of silicon PIN diodesand absorber layers

Size determined by rateabout 2 cm diameter

Full digital readout Active veto outside Passive shield around Veto

Shielding

Veto


The HEP Sensor System……Geometry

6 layers of sensors: 1st layer 2 sensors

of 50 m and 300 mwith coincidence

Other layers 300 m Increasing absorber-thickness:

10 m (pinhole), 200 m (ring) 0.8 mm, 1.6 mm, 3.2 mm, 6.4 mm, 12.8 mm

Protons will straggle to stop Electrons often have large angle scatters


The HEP Sensor System……Geometry

10 electronsgoing throughthe detector

Multiple scattering

Photonsproduced

Detector Sideview

e-


Radiation in Space……expected maximum fluxes

PROTONS ELECTRONS


Radiation in Space……expected LET rates for 1 cm2sr, 1mm Al

Helium:5 Hz - 15/day

Iron:0.07 Hz - 2/month

Iron shoulder 2•105 MeV/g/cm2

0.014 Hz - 4/year

Higher rates need much bigger surfaces

pHe

Fe

Fe

p HeCovered range


GEANT4 Simulation……Geometry

Full geometry implemented

6 mm Al-shield around active veto for low E particles

Height of detector adjustable

2 cm


GEANT4 Simulation……Setup

2 versions of simulation: ‘Old’ Simplified geometry, 20o input,

200 kEvents, flat spectrum, ROOT-histograms

Full geometry, full angle, 1 MEvents, ROOT-trees(available since mid september)

Most plots still with ‘old’ simulation Detailed analysis with ‘new’ simulation

currently ongoing (angular acc., veto-counters, power-law spectrum)


GEANT4 Simulation……Particle separation

Total E shown Protons very

cleanProtons

Electrons


GEANT4 Simulation……Proton binning < 80 MeV

5 bins by range in 1st 5 layers (3-80 MeV)

Excellent separation for range bins

Basically no cross-feed between energies


GEANT4 Simulation……Proton binning > 80 MeV

High E bins by total dE/dx

4 bins from 80 to 300 MeV

Good separation, easy unfolding of the small cross-feed

Last bin above 300 MeV as veto


GEANT4 Simulation……Electron binning

6 electron bins: 5 bins by range in

1st 5 layers, as for protons

Reasonable separation in E, unfolding needed

Last bin as veto for E > 14 MeV


GEANT4 Simulation……Electron/Proton separation

Good separation between electrons and protons/ions

Misidentification p e: < 6•10-5 at highest energy

Misidentification e p: 10-3 (low E)

10-2 (high E)

Color = Energy bins

High E

Low E

Electrons


GEANT4 Simulation……New Plots (ongoing)

Expected Angular Acceptance 20o

Crosscheck with simplified geometry show same behaviour

dE/dx unchanged

In sensor 1

No veto

Full angle

Preliminary


Outlook & Conclusions Range telescope shows convincing

performance from simulation Good e/p separation Spectra with reasonable binning

• Easy interpretation of proton spectra• Simple unfolding for electrons needed

Phase A finished, Phase B close to completion Fine tuning of simulation

Building of prototype detector will start 2006 Sensor samples already in our hands, will be

tested soon on probe station

Documents

GSEM project SPENVIS/GEANT4 Workshop, Leuven, Belgium, 3 - 7 October 2005 Daniel Haas, DPNC Genève Outline Description of GSEM HEP Range Telescope Radiation