LXe calibrations, PMT tests, cryostat construction

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LXe calibrations, PMT tests, cryostat construction

1. Alpha sources on wires
2. 9 MeV ? from neutron capture in Nickel
3. ?0
4. further calibration methods ?
5. PMTs tests
6. Cryostat status

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1) Alpha sources spots on wires

• Sorces at different distances seen by each PMT
  unique feature
• Made at Genova INFN
• electrodeposited ( solution) on
  a gold-plated W wire
• 0.5 mm spots 12.4 cm apart (2 PMTs)
• Wire thickness 50 ? (alpha range 40 ? )
• Wire suspended with springs
• Wires A,B 100 Bq/source (LP front face)
• Wires C,D 30 Bq/source (LP back face)
• A Czech Republic firm can provide a suitable wire
  in which Am on foils is attached to wires by
  thermocompression

LP Front face
Lateral face
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• The ring radius depends on the Rauleigh
  scattering length
• The best value for reproducing the radius is 20
  cm
• In contrast with previous estimates!
• Reflection ? ...we must improve the simulation
  and detector understanding

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• Small displacement of the two front wires

LXe
GXe
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PMT alpha direction
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Charge vs Cos? in LXe
Front Face
Data
MC
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LXe/MC
New PMTs
4 front sources
Old PMTs
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LXe/MC
4 front sources
After applying QEs
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Towards the final calorimeter
70 kHz photons with Egt5 MeV from muon radiative
decay _at_ R(?) 3x107. Total sources rate O(15 KBq
_at_ 5 MeV)
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Po half-life138 days

• Trigger was changed several times

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AMERICIUM WIRE-SOURCES

• World-wide search (from 2003...)
• ISOTRAK-AEA TECHNOLOGY
• ISOTOPE PRODUCTS
• LEA-CERCA
• NORTH AMERICAN SCIENTIFIC
• FRAMATOME
• ETC.
• all of them refused to consider this
  custom-made product....!
• too difficult, too long development, too
  expensive, etc.

Finally found a factory, Czech republic,
Prague working on ionization smoke detectors and
electrostatic charge eliminators (8 people.....)
accepted to perform a RD for our special
request. UP and DOWN
SUCCESS ! Production method by
thermocompression. Liquid Nitrogen tests at
ENEA. VERY IMPORTANT FOR FUTURE CRYOGENIC LIQUID
DETECTORS unique feature !
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SPECITICATIONS AND CONTRACT FOR THE PRODUCTION
OF Am WIRE-SOURCES AND OF Am DISK-SOURCES Ready
end of March 2005 (TOTAL ACTIVITY lt 40 kBq) Each
dot-source small radioative foil fixed on wire
by thermocompression TESTED AT NITROGEN
TEMPERATURE AT THE ENEA LAB. IN ROME. OK !

• NEEDED FROM PSI
• Authorization of nuclear security
• for products
• Authorization for import of
• radioactive sources
• Auhorization for production of
• detectors using radioactive sources

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WIRE SOURCES FOR FINAL CALORIMETER 15 WIRES, 5
DOT-SOURCES PER WIRE
150 cm total wire length
12.4 cm distance between Am dots
Central Dot
20.0 cm distance between Mark and First Dot
Am dots
Reference Mark
Wire of ?100 micron diameter Material gold
plated steel or tungsten Total length 150
cm Spacing of dot-sources 12.4 cm Linear
dimension of dots 1-2 mm Activity ? 200 Bq per
dot
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WIRE SOURCES FOR LARGE PROTOTYPE 10 WIRES, 2
DOT-SOURCES PER WIRE
150 cm total wire length
12.4 cm distance between Am dots
Wire centre
Am dots
20.0 cm distance between Mark and First Dot
Reference Mark
Wire of ?100 micron diameter Material gold
plated steel or tungsten Total length 150
cm Spacing of dot-sources 12.4 cm Linear
dimension of dots 1-2 mm Activity ? 200 Bq per
dot
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WIRE SOURCES FOR PISA DEVICE 2 WIRES, 1
DOT-SOURCE PER WIRE
50 cm total wire length
Reference Mark
Central Am Dot
20.0 cm distance between Mark and Dot
Wire of ?100 micron diameter Material gold
plated steel or tungsten Total length 50
cm Central dot-source Linear dimension of
dots 1-2 mm Dot Activity ? 200 Bq
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rather narrow energy-spectra possible mounting
on special supports and screws
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Will it be possible to use them _at_ beam on?
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2) 9 MeV gamma line from neutron capture on
NickelExperimental set-up

• Am-Be source
• (20000 n/s)
• Polyethylene
• Nickel plates
• 30 x 30 cm2
• (0.5 cm and 0.25 cm
• thickness)
• 20 x 20 x 36 cm3
• NaI detector
• MCA ORTEC
• (2048 channels)
• NIM electronics.

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?-line from n-capture on Ni, I, Al, H2 natural
radioactivity Tl, K Am/Be source
Am/Be 4.4 MeV 1st escape
Ni 8.54 MeV 1st escape
H2 2.2 MeV
K 1.46 MeV
Tl 2.6 MeV
I 6.8 Mev
Ni 9 MeV
Al 7.7 MeV
Black Am/Be source and 1 cm Ni Red no
Am/Be source Green no Am-Be source, no Ni (Gotta
Beam on)
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neutron generator (Pavia ?)
THERMAL NEUTRON CAPTURE ON NICKEL
D 2H ? 3He n Q 3.27 MeV D 3H
? 4He n Q 17.59 MeV

• Potentialities
• switchable on-off
• frequent (s, m,...) stability checks
• system out of the calorimeter
• Ni and Xe, prompt and delayed signals
• probably visible signal at full beam intensity
• time reference

9 MeV Nickel ?-line

• Open problems
• monitoring from calorimeter back
• only at one location ?
• some dispersed neutrons and radioactivity
• test of the method at high beam intensity
• useful test with the large prototype
• (already foreseen in April, with Am/Be source)

NaI 20 x 20 x 36 cm3

• Intensities from 106 n/s to 108 n/s
• Typical pulse rate and pulse width 10 Hz and 1
  µs
• Time separation of direct from delayed reactions
• Single pulse mode

Polyethylene
0.25 cm Nickel plate
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Possibilities
POLY
POLY
POLY
POLY
POLY
NaI
n
Am/Be
0.25 cm Nickel
3 cm polyethylene
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3) p0 calibration
How often can it be performed?
Anti Counter
Support structure straightly up and down Tilt
mechanism at every height for NaI front to face
target direction.
tilt

• Proton beam 1.8mA
• Pion Rate 2x107 p-/sec
• Collimate 2PMTs x 2PMTs 150cm2
• (1 position)
• 2 g/sec
• of PMTs on incident face 216 PMTs (54
  positions)
• required 30,000 evts/position
• takes 30,000 x 54 / 2
• 810,000sec 10 days

g
Target
up
p0
down
g
target
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3) Further calibration methods... 500 KV PROTON
ACCELERATOAND LITIUM TARGET FOR A 17.6 MEV GAMMA
LINE
37Li (p,?)48Be
P.R. 73, 666 (1948), N.P. 21 1 (1960),
Zeitschrift f. Physik A351 229 (1995)

• Potentialities
• a unique nuclear reaction with a high energy ?
  -line (??10 KeV)
• obtainable ? 106 ?/s (isotropic) at 440 KeV
  resonance (Ip? 50 ?A)
• from LiF target at COBRA center ?s on the
  whole cal. entrance face
• energy and position calibration shower
  properties all over LXe cal.
• possibly rather frequent use

• Open problems
• compatibility with normal beam and target ?
• project for easiness of target-tube mounting
• accelerator/COBRA, which position and distance ?
  
• p-beam divergence and protons on target p?29
  MeV/c
• 500 KeV and criticality of an air-insulated
  accelerator
• is a post-acceleration possible ?

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Previously used...
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37Li (p,?)48Be
resonant at Ep 440 keV ?14 keV ?peak 5
mb E?0 17.6 MeV E?1 14.6 6.1 Bpeak
?0/(?0 ?1) 0.72?0.07
NaI 12x12 ? spectrum
Crystal Ball Data
?0
?1
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A further interesting possibility...
Cecil et al. NP A539 75 (1992) 10x10 cm NaI
crystal
511B (p,?)612C
resonant at Ep 163 keV ? 7 keV E?0 16.1 MeV
?peak 5.5 ?b E?1 11.7 4.4 ?peak 152
?b

• ? 750 ?0/s (isotropic)
• 20.000 ?1/s for Ip? 50 ?A

lower proton energy ! lower rate at 50 ?A !!
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NOW GLAST SPACE EXPERIMENT CRYSTAL CALORIMETER
CALIBRATION
180 cm target-pipe
It is the old VDG of the Crystal Box experiment !
! they have some problems old device, max. VDG
p-energy is 400 KeV out of resonance ?-rate
reduced by factor ? 5000 How can we get one
such device ?? We are exploring several
possibilities...
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Cal. calibration from the target position,
monitoring at the cal. back
rails
cockroft
focusing elements (magnetic or electrostatic ?)
at the cal. back the proton motion in the COBRA
field must be be studied
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proton MC trajectoriesEp ?440 keV ? ?28 MeV/c !!
Y(cm)
the protons are not reflected back by the
varying magnetic field T 8? ? giroradius lt 12
cm
X(cm)
Z(cm)
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Plane Z 0 cm
Y(cm)
? 0.8cm
X(cm)
T 0.5? ? giroradius lt 1 cm
Z(cm)
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KEEP MEG UNDER CONTROL PARTICULARLY AT HIGH
(AND VARIABLE) BEAM INTENSITIES.........
BR ? ? e g 10-13
Beam Intensity5 107 ?/s

• frequent checks of calorimeter energy scale,
  linearity and stability
• checks of LXe optical properties
• energy resolution and spacial resolution
• shower properties
• at the right ? energy (? 53 MeV), but also at
  other energies.....

no single calibration method has all the required
characteristics use complementary (and redundant)
methods, make the best use of their intrinsic
properties emphasize the reliability of our
experiment
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5) PMT tests
PMT in LP, LED pulsed (_at_ 1 khz)
F18, TB type
F0, 6041 (old)
ltQgt 50 pC
ltQgt 87 pC
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10 Khz
TB
6041
ltQgt 50 pC
ltQgt 87 pC
photocathode saturation effect
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50 Khz
6041
TB
ltQgt 50 pC
ltQgt 87 pC
photocathode saturation effect
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100 Khz
6041
TB
ltQgt 50 pC
ltQgt 87 pC
Gain non linearity
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6041
t 115 s
Anode current should be lt 0.5 mA
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TB
Lower photocathode resistivity (ZA much better)
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Zener Diodes on PMT Base
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Linearity much improved
presently installed
T-108ºC
PMT with Zener
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But Zener problem at low temperature

• Positive pulses with total positive charge are
  seen! (rate 300 Hz _at_ Vgt20 mV)
• The problem is present ONLY at liquid Xe
  temperature disappears during warm-up
• The pulse is not present when the Zener diodes
  are removed

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Several Zener diode types tried
Seller Brand Package
Distrelec FairChild Glass
Farnell Phillips plastic
RS On semicond plastic
RS Phillips Ceramic
Original ... plastic
RS Vishay sinter gl.
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Results FairChild
6875 5 Hz
7575 200 Hz
(75//75)x2 3 Hz
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R9288 base with low pass filter

• Low pass filter is built in
• by adding resistors serial to Zener

• If the resistance is too small, filtering will
  not work.
• With too large resistance, the effect of Zener
  will be little
• under high rate BG environment

Optimum resistance will be something around
100KOhm
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Low pass filter in PMT base _at_ Astro-E2 HXD

• PMT base with Zener diode and low pass filter is
  adopted in Astro-E2 Hard X-ray Detector. (HXD)
• Fifth Japanese space X-ray observatory
• PMTBGO
• High counting rate
• HXD will be cooled downed to 30 C

Zener is used in this base circuit and low pass
filter is built in because of the noise from
Zener. Various tests have been performed with
this base and its good performance was confirmed
so far.
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PMT Test using the base with Low Pass filter
Type Z
Type ZR
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Chamber Set Up
Type Z
Upper PMT temp. - 85 C
HV800V for both PMTs Same interstage volt.,
same current between 2 PMTs
Alpha source LED
Type ZR
Gas xenon
Lower PMT temp. - 100 C
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Oscilloscope Snapshot
Noise from Zener
Type Z
No noise was observed!!
Alpha event
Type ZR
Yasuko HISAMATSU MEG Collaboration Meeting Feb.
2005
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If the base Type ZR doesnt work

• We have an alternative active base with MOS-FET
• Adopted in the pß experiment
• MOS-FET is operational in 165K

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When a solution is found
Start testing PMTs 300-400 at Pisa (Cryo
facility) and 600-700 at PSI (LP)
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6) Cryostat designs ready tenders and
procurements organization

• Tenders have been organized in three parts
• Conventional part
• Cold and warm windows
• Purchasing of the cold sealing
• PMTs supporting structure
• The tender procedure has been completed for the
  conventional part.
• SIMIC has won the tender for the best price and
  for other reasons.
• This company is going to purchase a low magnetic
  permeability stainless steel (lt1.008) and will
  perform the cold test at the company. We visited
  the company to warn them about the project
  difficulty, remarking our requirements in term of
  level of cleanness and tightness written in the
  tender technical specification.
• The company, if it will receive in time the cold
  and warm window and the cold sealing, estimated a
  fabrication time of 10th month.

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SIMIC profile in cryogenics application
http//www.simic.it/eng/home.htm
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Cold and warm windows

• FEA studies are in progress.
• Honeycomb structure has been discussed with
  manufacturing companies

• We are trying to subdivide the fabrication and
  qualification of the window to be able to
  maintain the cost as low as possible
• We have separated the following activities.
• Mechanical test ( Mech. Dept Univ of Pisa)
• Test box and welded parts (Mechanical design
  INFN (Pisa) manufacturing with proper company)
• Tooling and molds are going to be designed by
  INFN (Pisa)
• Honeycomb structure (Composite aerospace
  company)

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FEA studies are in progress
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Honeycomb structure discussed with manufacturing
company
Honeycomb structure Two facing of .7 mm
CFRP. (intermediate high module CF with Epoxy
space approved) Core aluminum honeycomb perforated

Internal welded foil .3 mm or less welded on
external Frame necessary to test the window prior
the final welding on the cryostat body.
This area is reinforced
Bolted area
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Honeycomb structure has been discussed with
manufacturing company
Using thin facing material makes difficult to
obtain high tolerance, even if we use a flex core
material, not available in perforated aluminum.
This area is reinforced
Precision must been obtained on this side for
this reason the honeycomb must rest on the mold
on this side
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Cold joints interaction with the factory
Modification of bolts position and number
We asked non-magnetic seal
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Pisa 30-December-2004
Cold joints
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PMTs supporting structure design
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Some issues recently reviewed

• Detailed drawings of internal attachments
• Windows area dimensions reviewed.
• Superinsulation required to the company
• Electro polishing of internal surfaces
• Outer vessel isolated from the base. (A G10 plate
  will be placed under the cryostat legs)
• Reviewed the height of all components
• Metallic o-rings to be fixed in the vertical
  position
• Guiding pins needs to be added on the cold and on
  the warm flange to avoiding that the studs are
  hitting the contact surface of the o-ring on the
  covers

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2005
Calorimeter schedule
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Neutron measurements status
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