1. technology and computing

DEGAS Detector
Status report
I. Kojouharov, GSI, Darmstadt
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
1. Status of the Cryostat development
2. Cooling engine
3. BGO Element
4.
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
1. Status of the Cryostat development
Backcatcher Element:
BGO Crystal (BGO)
Housing (Al)
Cold frame (Al)
Preamplifier lid (plastic)
Detector head lid (Al)
Capsule lid (Al)
Capsule (Al)
Detector head end cap (Al)
HPGe Crystal (Ge)
DEGAS Detector head
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
1. Status of the Cryostat development
Improved thermal contact junction
DEGAS capsules cold frame
NUSTAR week, 2015 , March 02-06,
GSI
Here to be installed additionally SAES NGO
getter tabs for vacuum improvement
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
1. Status of the Cryostat development
DEGAS end cap
Hexagonal geometric polarization and structural
stabilization fixture
DEGAS detector lid
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
2. Cooling engine
Cooling fins
Test fixture
Under test:
- strong cooling power
- heavy energy dissipation – need
air cooling with a defined flow. An
option – cooling jacket.
- strong vibrations. There is a
vibration reductor and this option is
to be investigated. The detector
construction has to consider
vibration strong reduction if not an
elimination.
Controller
48 V power supply
NUSTAR week, 2015 , March 02-06,
GSI
Sunpower cooling engine Type GT:
- 16 W cooling power
- 240 W electrical
Conclusion: the use of SP GT or
CT cooling engines needs further
R&D, therefore initially the MMR XCooler has to be considered and
an interface for easy transition to
SP CT-cooler to be provided.
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
2. Cooling engine
Compressor
Connecting pipeline, 3 m,
No twisting, limited radius bending
X-Cooler II, MMR/ORTEC
Cooling head
PopTop capsule
.
But only for PopTop Capsules..
Conclusion: the use of SP GT or
CT cooling engines needs further
R&D, therefore initially the MMR XCooler has to be considered and
an interface for easy transition to
SP CT-cooler to be provided.
X-Cooler II or III, MMR/ORTEC approx. 11 W
cooling power, 240 VAC/500 VA Power
MMR XC
SP CT
Cooling (total) power
11 W (240V/500W)
11W (24V/120W)
End temperature
-187 °C
-220 °C
Vibrations
very low
high
Life
unknown, 3-7 Years
unknown, >200 000 h
Compactness
low
high
Functionality
medium
medium
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
3. BGO Element
BGO Backcatcher:
- Good coverage of the Ge-crystals.
In contrast to the EB-Cluster where
the inner capsule is not BGOcovered, here the three capsules
assembly is a challenge.
- Made out of 3 elements
- Crystal thickness of 50 mm –
reuse of the EB-backcatcher
- Separate fixing to the cryostat
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
3. BGO Element – crystal readout
BGO BC with 2 x 1.5‘‘ Hamamatsu phototube
BGO BC with 1 x 2‘‘ Hamamatsu phototube
2 x 1.5‘‘ PMT
1 x 2‘‘ PMT
SiPM C-serie
Area coverage
46 %
36 %
26 %
QE
10-15 %
10-15 %
35-40 %
Uniformity
medium
low
high
Height
80 mm
120 mm
10-15 mm
HV
1000-2500 V
1000-2500 V
25-30 V
cost
2 x 1500 (?) Euro
1 x 3500 (?) Euro
70 x 28 (18?) Euro
NUSTAR week, 2015 , March 02-06,
GSI
DEGAS Detector
I. Kojouharov, GSI, Darmstadt
4. Timeline
Cryostat design:
- Until end of July-mid August full set of production drawings.
- Until end of August – some critical components – end cap, cold frame, end cap lid,… (?)
- Until end of November – component production (?)
NUSTAR week, 2015 , March 02-06,
GSI
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
1. DEGAS – the DESPEC HPGe array
The DESPEC TDR defines three phases
of project evolution:
I Phase: Array made of seven- or three-fold
encapsulated and unsegmented HPGe
crystals assemblies;
II Phase: Array enforced by the highly
sedmented AGATA detectors;
III Phase: New planar detectors based array
with an enhanced imaging capability
Phase III is still outside the funding frame of
DESPEC array and, despite some
developments as the cryostat etc., needs
considerably more R&D to become fit for
physics tasks.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Quasi-planar prototype
Ge diode.
Planar detector cryostat developed
in Sofia
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
1. DEGAS – the DESPEC HPGe array
The possible geometries:
Half sphere
EB Clusters based
shell
Triples base
box
Triples based
The box configuration based on triples and AIDA “long” configuration
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
1. DEGAS – the DESPEC HPGe array
Some constraints
1. Physical:
- The geometry
2. Functional:
- Too small dewar would require
too frequent filling – LN2 boiling
interference, reliability, too little
time for reaction by alert etc.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
The spherical geometry The “box” geometry
tolerates any size of the does not, the dewar
diameter must be no
dewar
larger of the detector
head size.
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
2. LN2 cooling vs. electrical cooling
LN2 cooling:
- mature inexpensive technology
- large cooling power
- well developed component basis and
supply infrastructure
LN2 cooling (dewar) or electrical cooling?
Electrical cooling
- Long term unattended operation and space constraints.
Applications requiring unattended operation and space constraints (too little place for the dewar etc.)
- Enhanced functionality
LN2 based cooling technology must consider logistic issues – Autofill System, LN2 Tank, Pipeline, Filling lines,
Control etc. The Electrically cooled Composite Detectors would require much less efforts by their operation
- Hazard reduction !!
Cost estimates (2-3 fillings per day, 6-12 l per detector per filling), 32 ch., group of 8 ch. per buffer tank
Dewar – 1-5 k€
Cooling engine: 12-18 k€
Filling channel – 6-8 k€
Monitoring and power, CFC :
1 k€
Buffer Tank, CFC – 2 k€
Pipeline (1 k€/m), 160 m, CFC – 5 k€
Safety, CFC – 1-3 k€
--------------------------------------------------------------------------------Total, CFC – 23 k€ +/- 4 k€ WCS
19 k€ +/- 2 k€ WCS
CFC – Cost Fraction per Channel
NUSTAR week, 2014 , September
22-26, Valencia, Spain
WCS – Worst Case Scenario
LN2 price = electricity price
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
2. LN2 cooling vs. electrical cooling
Cooling engines:
X-Cooler II, MMR/ORTEC
.
But only for PopTop Capsules..
X-Cooler II or III, MMR/ORTEC
approx. 11 W cooling power,
240 VAC/500 VA Power
NUSTAR week, 2014 , September
22-26, Valencia, Spain
SunPower Type GT, SunPower
Type GT – 16 W, type CT – 11 W
cooling power, 48 VDC/300 W (GT)
and 24VDC/110 W Power
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
3. Thermodynamics of HPGe detector
The radiative transfer in the detector assembly is
determined by the heat exchange between the outer parts
of the cryostat which are at room temperature and the
inner cold structure which is at near liquid nitrogen
temperature by infrared rays. The path of the transfer
leads through the cold finger to the heat reflector and
further to the detectors housing which holds the Ge
crystals.
Thermal bridges are the mechanical components used
for fixing the cold structure to the warm section of the
cryostat and the internal cabling between the crystal
housing and the vacuum feedthroughs. The heat exchange
is realized by thermoconductivity.
Thermodynamic model of the detector
NUSTAR week, 2014 , September
22-26, Valencia, Spain
The residual gas heating takes place typically at low
vacuum, however the specifics of the process must be
taken into account.
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
3. Thermodynamics of HPGe detector
Radiative transfer effects
Temperature distribution along the Ge-capsules
and the cold finger when the temperature of the
cooling part is 70 K and the ambient temperature
is 295.15 K. The emissivity of the Ge-capsules is
0.2, when the emissivity of the processed inner
surface of the cryostat is 0.1. The total heat
transfer (including the cold frame) is about 3 W.
Courtesy of J.Kojouharova
Only increase of the ambient temperature in three degree causes increase of the total heat losses with 3.3
%. If the ambient temperature increases once again with five degree more, the heat losses increase with
10.2 %.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
3. Thermodynamics of HPGe detector
Radiative transfer effects
Courtesy of J.Kojouharova
The radiative absorbed heat by the detector head vs. the gap width between
the housing and the cold structure. The data plotted on left a are calculated for
εh=0.6 and three different εdh, while on right the heat absorbed at detector
head emissivity taken to be 0.1 and various housings emissivity is presented.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
3. Thermodynamics of HPGe detector
Thermal conductivity effects
Temperature distribution along the
cold finger (D=24 mm, L=700 mm)
interface. Temperature at the cold
part is 100 K and the heat losses at
the warm part are 3 W.
Courtesy of J.Kojouharova
Temperature profile at the fixing component surface vs.
the topology. The topology proposed results in only 50
mW heat losses and good mechanical stability.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
3. Thermodynamics of HPGe detector
Vacuum effects
Courtesy of J.Kojouharova
Heat flux behavior vs. residual gas pressures. Three different residual gas pressure intervals are
important: lower than 1E-4 mbar, where the heat flux is “insensitive” to the gap width, between 1E-3
mbar and 1E-4 mbar being week function on gap width and above 1E-3 mbar, where strong impact of
the gap width can be seen.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
3. Thermodynamics of HPGe detector
Thermal timeout.
Temperature development
in dependence on detector
configuration and ε=0.2
(left) and ε=0.1 (right).
Here the temperature of
the cold part is considered
to be 77 K, while the
temperature of the warm
part 300 K.
Courtesy of J.Kojouharova
Warming up of a single HPGe detector with
15 % efficiency (commercially available
PopTop), which corresponds of 344 g Ge.
The warm up time is evaluated based on
typical crystal housing
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
4. Electrically cooled massive detectors and compositions
Single capsule detector.
X-Cooler head
Electronics cover
Cold frame
Getter Container
Flanges
Detector cup
Detector capsule
Ge-crystal
Cold finger I Section
Cold finger II Section
Indium support
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Main Getter
Container
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
Single capsule detector.
FWHM [keV]
6. Electrically cooled massive detectors and compositions
4,0
1332 keV
122 keV ORTEC 672
60 keV
3,5
1332 keV
122 keV IN7243
60 keV
3,0
2,5
2,0
1,5
1,0
0,5
0,0
0
2
4
6
8
Shaping Time [µs]
Energy resolution of HEX 146 vs. shaping time.
Energy resolution at 1332 kev and LN2 cooling in
Lab – 1.96 keV (GSI cold board !)
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
6. Electrically cooled massive detectors and compositions
PANDA GErmanium Array (PANGEA) - consist of 48 encapsulated HPGe detectors. The detector is
currently under development in GSI. The head geometry is similar to the DEGAS detector head.
Too short distance
to the barrel wall.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
6. Electrically cooled massive detectors and compositions
Flexible cold finger and flexible cold finger
tube. Allows full use of the space available for
detectors.
Detector Head fixing.
Electronics chamber
X-Cooler Head, partially hidden inside
the electronics chamber
The PANGEA triple detector is based on encapsulated HPGe crystals (EB capsules). The
detector features flexible neck facilitating closed positioning to the barrel walls and integrated
electronics – preamplifier, power supply, HV and monitoring.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
6. Electrically cooled massive detectors and compositions
DEGAS Triple detector
Cooling engine.
XC2 id displayed,
but SunPower GT
or CT is also OK.
Backcatcher
place
Cold Frame
EB capsule
The DEGAS Triple detector is based on PANGEA triple and features rigid neck with certain length in
order to facilitate installation of the backcatchers, integrated electronics – preamplifier, power supply, HV,
monitoring and possibly digitalization, pre-DAQ and data transfer. Backcatchers are based on the EB
backcatchers remade onto 3 segments with SiPM readout.
NUSTAR week, 2014 , September
22-26, Valencia, Spain
Electrically cooled HPGe
detectors NUSTAR
I. Kojouharov, J.Gerl, GSI, Darmstadt
Thank you.
NUSTAR week, 2014 , September
22-26, Valencia, Spain