Transcript GSEM project SPENVIS/GEANT4 Workshop, Leuven, Belgium

GSEM project
SPENVIS/GEANT4 Workshop,
Leuven, Belgium, 3 - 7 October 2005
Daniel Haas, DPNC Genève
Outline
 Description of GSEM
 HEP Range Telescope
 Radiation in Space
 GEANT4 Simulation
 Outlook & Conclusions
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

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 2
…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

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 3
…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

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 4
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
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 5
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

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 6
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:
 Protons:
 Ions:

120 keV - 7 MeV
3 MeV - 300 MeV
1 - 70 MeV/cm2/mg
Viewing angle at least  20o
 Sampling rate: 500 kEvents/s with dead
time correction

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 7
The HEP Sensor System…
…Design Approach

Range Telescope with:

Measured quantities:
• Range
• dE/dx in all layers
Stack of silicon PIN diodes
and absorber layers
 Size determined by rate
about 2 cm diameter
 Full digital readout
 Active veto outside
 Passive shield around Veto
Shielding

Veto
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 8
The HEP Sensor System…
…Geometry

6 layers of sensors:
1st layer 2 sensors
of 50 m and 300 m
with 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

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 9
The HEP Sensor System…
…Geometry
10 electrons
going through
the detector
 Multiple
scattering
 Photons
produced
Detector Sideview

e-

SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 10
Radiation in Space…
…expected maximum fluxes
PROTONS
ELECTRONS
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 11
Radiation in Space…
…expected LET rates for 1 cm2sr, 1mm Al

Helium:
5 Hz - 15/day
Covered range
p
p
He
He

Iron:
0.07 Hz - 2/month
Fe

Iron shoulder
2•105 MeV/g/cm2
0.014 Hz - 4/year
Fe

Higher rates
need much
bigger surfaces
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 12
GEANT4 Simulation…
…Geometry

2 cm


Full geometry
implemented
6 mm Al-shield
around active veto
for low E particles
Height of detector
adjustable
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 13
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., vetocounters, power-law spectrum)
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GEANT4 Simulation…
…Particle separation
Total E shown
 Protons very
clean

Protons
Electrons
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 15
GEANT4 Simulation…
…Proton binning < 80 MeV


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5 bins by range in
1st 5 layers
(3-80 MeV)
Excellent
separation for
range bins
Basically no
cross-feed
between energies
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 16
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 crossfeed
Last bin above
300 MeV as veto
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 17
GEANT4 Simulation…
…Electron binning



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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
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 18
GEANT4 Simulation…
…Electron/Proton separation

Color = Energy bins
High E


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)
Low E
Electrons
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 19
GEANT4 Simulation…
…New Plots (ongoing)


dE/dx unchanged
Expected Angular
Acceptance  20o
Crosscheck with
simplified geometry
show same
behaviour
No veto
In sensor 1
Full angle
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 20
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


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Fine tuning of simulation
Building of prototype detector will start 2006
Sensor samples already in our hands, will be
tested soon on probe station
SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 21