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February 9th 200511
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
Calibrations
22
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
February 9th 200555
•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
1111
70 kHz photons with E>5 MeV from muon radiative decay @ R() 3x10**7. Total sources rate O(15 KBq @ 5 MeV)
Towards the final calorimeter
February 9th 20051313
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, Pragueworking on ionization smoke detectors and electrostatic charge eliminators
(8 people.....)
accepted to perform a R&D for our special request. UP and DOWN SUCCESS !:
Production method by “thermocompression”. Liquid Nitrogen tests at ENEA.
VERY IMPORTANT FOR FUTURE CRYOGENIC LIQUID DETECTORSunique feature !
February 9th 20051414
SPECIFICATIONS FOR THE PRODUCTION OF SEVERAL Am WIRE-SOURCES
AND SEVERAL Am DISK-SOURCES January 5th 2005
The wire sources should be produced according to the 3 model drawings “final calorimeter” (15 wires), “large prototype” (8 wires), Pisa device (2 wires). Final calorimeter: 15 wires, 5 dot-sources per wire,Large prototype: 10 wires, 2 dot-sources per wire, Pisa device: 2 wires, a single dot source The Am dots should be mounted by thermocompression on a gold plated steel or tungsten wire of diameter 100 m. The resulting wire diameter, after the source mounting, should be < 200 m. The source surface should be as smooth and regular as possible. The dot sources should be covered by a protective gold layer 1.5 m thick. The activity of each Am dot should be about 200 Bq with a tolerance 25%. Each dot should have a linear dimension < 2 mm. The position of each dot on the wire should be precise within 1 mm. A reference mark (non radioactive !) should be mounted on one side of the wire only; the mark (perhaps a gold layer fixed by thermocompression) should be easily visible. The wires must be shipped without damaging them; each wire could perhaps be mounted on a thin plastic rod or wrapped around a large diameter spool. The 25 disk-sources should be gold plated disks of diameter 5 mm and have an activity of 500 Bq per source. Each source should be covered by a protective gold layer 1.5 m.
SPECITICATIONSAND CONTRACT
FOR THE PRODUCTION OF Am WIRE-SOURCES AND
OF Am DISK-SOURCESReady: end of March 2005
(TOTAL ACTIVITY < 40 kBq)
Each dot-source: small radioative foil fixed on wire by
“thermocompression”
TESTED AT NITROGEN TEMPERATUREAT 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
February 9th 20051515
Wire of 100 micron diameterMaterial: gold plated steel or tungsten Total length 150 cmSpacing of dot-sources 12.4 cmLinear dimension of dots 1-2 mmActivity 200 Bq per dot
150 cm total wire length
Am dots
12.4 cm distance between Am dots
Reference Mark
20.0 cm distance between Mark and First Dot
Central Dot
WIRE SOURCES FOR FINAL CALORIMETER15 WIRES, 5 DOT-SOURCES PER WIRE
February 9th 20051616
Wire of 100 micron diameterMaterial: gold plated steel or tungsten Total length 150 cmSpacing of dot-sources 12.4 cmLinear dimension of dots 1-2 mmActivity 200 Bq per dot
150 cm total wire length
Am dots
12.4 cm distance between Am dots
Reference Mark
20.0 cm distance between Mark and First Dot
Wire centre
WIRE SOURCES FOR LARGE PROTOTYPE10 WIRES, 2 DOT-SOURCES PER WIRE
February 9th 20051717
Wire of 100 micron diameterMaterial: gold plated steel or tungsten Total length 50 cmCentral dot-source Linear dimension of dots 1-2 mmDot Activity 200 Bq
50 cm total wire length
Reference Mark
20.0 cm distance between Mark and Dot
Central Am Dot
WIRE SOURCES FOR PISA DEVICE2 WIRES, 1 DOT-SOURCE PER WIRE
February 9th 20052020
Will it be possible to use them @ beam on?Will it be possible to use them @ beam on?
February 9th 20052121
2) 9 MeV gamma line from neutron capture 2) 9 MeV gamma line from neutron capture on Nickelon Nickel:Experimental set-upExperimental set-up
- Am-Be source Am-Be source (20000 n/s);(20000 n/s);
- Polyethylene;Polyethylene;
- Nickel platesNickel plates 30 x 30 cm30 x 30 cm22 ((0.5 cm0.5 cm and and 0.25 cm0.25 cm thickness)thickness) - 20 x 20 x 36 cm20 x 20 x 36 cm33 NaI detectorNaI detector
-MCAMCA ORTECORTEC (2048 channels)(2048 channels)
- NIM electronics.NIM electronics.
February 9th 20052222
γ-line from n-capture on Ni, I, Al, H2; natural radioactivity Tl, K; Am/Be source
Am/Be4.4 MeV &1st escape
I6.8 Mev
Al7.7 MeV
Ni9 MeV
Ni8.54 MeV &1st escape
H2
2.2 MeV
Tl2.6 MeV
Black: Am/Be source and 1 cm Ni Red: no Am/Be sourceGreen: no Am-Be source, no Ni(Gotta Beam on)
K1.46 MeV
February 9th 20052323
9 MeV Nickel γ-line
NaI 20 x 20 x 36 cmNaI 20 x 20 x 36 cm33
neutron generator (Pavia ?)
• 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
THERMAL NEUTRON CAPTURE ON NICKEL
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
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)
D + 2H 3He + n Q = 3.27 MeV
D + 3H 4He + n Q = 17.59 MeV
Polyethylene
0.25 cm Nickel plate
3 cm 20 cm
February 9th 20052424
PossibilitiesPOLY POLYPOLY
Am/Be
0.25 cm Nickel
n
POLY POLY
3 cm polyethylene
NaI
February 9th 20052525
3)0 calibration…
Target
Anti Counter
up
tilt
down
Support structure: straightly up and downTilt mechanism at every height for NaI front to face target direction.
target
00
• Proton beam: 1.8mA
• Pion Rate: 2x107 -/sec
• Collimate: 2PMTs x 2PMTs ~ 150cm2
(1 position)
• 2 /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
How often can it be How often can it be performed?performed?
February 9th 20052626
3) Further calibration methods... 500 KV PROTON ACCELERATOAND LITIUM TARGET FOR A
17.6 MEV GAMMA LINE
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; p29 MeV/c • 500 KeV and criticality of an air-insulated accelerator• is a post-acceleration possible ?
[P.R. 73, 666 (1948), N.P. 21 1 (1960), Zeitschrift f. Physik A351 229 (1995)] 3
7Li (p,)48Be
February 9th 20052828
37Li (p,)4
8Be
resonant at Ep= 440 keV =14 keV peak = 5 mbE0 = 17.6 MeVE1 = 14.6
6.1Bpeak 0/(0+ 1)= 0.720.07
NaI 12”x12” spectrum
1
0
Crystal Ball Data
February 9th 20052929
511B (p,)6
12C
lower proton energy !lower rate at 50 A !!
A further interesting possibility...Cecil et al. NP A539 75 (1992)10x10 cm NaI crystal
resonant at Ep= 163 keV= 7 keVE0 = 16.1 MeV peak = 5.5 bE1 = 11.7 + 4.4 peak = 152 b
750 0/s (isotropic) 20.000 1/s for Ip 50 A
February 9th 20053030
NOW: GLAST SPACE EXPERIMENTCRYSTAL CALORIMETER CALIBRATION
It is the old VDG of the Crystal Box experiment ! !they have some problems: old device, max. VDG p-energy is 400 KeVout of resonance: -rate reduced by factor 5000 How can we get one such device ?? We are exploring several possibilities...
180 cm target-pipe
February 9th 20053131
rails
cockroft
focusing elements(magnetic or electrostatic ?)
Cal. calibration from the target position, monitoring at the cal. back
at the cal. back the proton motion in the COBRA field must be be studied
February 9th 20053232
proton MC trajectoriesEp 440 keV 28 MeV/c !!
Z(cm)
X(cm)
Y(cm) the protons are not reflected back by the varying magnetic field
Θ ~ 8 giroradius < 12 cm
February 9th 20053434
KEEP MEG UNDER CONTROL
PARTICULARLY AT HIGH (AND VARIABLE) BEAM INTENSITIES.........
• 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
BR e ~10-13 Beam Intensity~5 107 /s
February 9th 20053535
5) PMT tests
<Q> = 50 pC
F18, TB type F0, 6041 (old)
<Q> = 87 pC
PMT in LP, LED pulsed (@ 1 khz)
4343
But … Zener problem at low temperature
•Positive pulses with total positive charge are seen! (rate ~300 Hz @ V>20 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
4444
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.
February 9th 20054646
R9288 base with low pass filter
Optimum resistance will be something around 100KOhm
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
February 9th 20054747
Low pass filter in PMT base @ Astro-E2 HXDPMT base with Zener diode and
low pass filter is adopted in Astro-E2 Hard X-ray Detector. (HXD)
Fifth Japanese space X-ray observatoryPMT+BGOHigh counting rateHXD 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.
February 9th 20054949
Chamber Set Up
Type ZR
Gas xenon
Alpha source LED
Type Z
Upper PMT temp.
~ - 85 °C
Lower PMT temp.
~ - 100 °C
HV=800V for both PMTsSame interstage volt., same current between 2 PMTs
February 9th 20055050
Oscilloscope SnapshotType Z
Type ZR
Yasuko HISAMATSU MEG Collaboration Meeting Feb. 2005
No noise was observed!!
Noise from Zener
Alpha event
February 9th 20055151
We have an alternative; active base with MOS-FET
Adopted in the πβ experiment MOS-FET is operational in 165K
If the base Type ZR doesn’t work…
February 9th 20055252
When a solution is found
Start testing PMTs: 300-400 at Pisa (Cryo facility) and 600-700 at PSI (LP)
February 9th 20055353
6) Cryostat: designs ready; tenders and procurements organization
Tenders have been organized in three parts:1. Conventional part2. Cold and warm windows3. Purchasing of the cold sealing 4. 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 (<1.008) 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.
February 9th 20055555
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)
February 9th 20055656
FEA studies are in progress
0
0,00005
0,0001
0,00015
0,0002
0,00025
0,0003
0,00035
0,0004
0,00045
0,0005
0,0003 0,0004 0,0006 0,001
thickness ( m )
max
dis
plac
emen
t ( m
)
incastro max displ-thickness cerniera max displ-thickness
0
20000000
40000000
60000000
80000000
100000000
120000000
140000000
160000000
180000000
200000000
0,0003 0,0004 0,0006 0,001
thickness ( m )
max
prin
cipa
l ( P
a )
cerniera max princ-thickness membrane theory
0
20000000
40000000
60000000
80000000
100000000
120000000
140000000
160000000
180000000
200000000
0,0003 0,0004 0,0006 0,001
thickness ( m )
max
prin
cipa
l ( P
a )
Incastro max princ-thickness membrane theory
February 9th 20055757
Honeycomb structure discussed with manufacturing company
Internal welded foil .3 mm or less welded on externalFrame necessary to test the window prior the final welding on the cryostat body.
Bolted area
This area is reinforced
Honeycomb structureTwo facing of .7 mm CFRP.(intermediate high module CF withEpoxy space approved)Core aluminum honeycombperforated
February 9th 20055858
Honeycomb structure has been discussed with manufacturing company
Precision must been obtained on this side for this reason the honeycomb must rest on the mold on this side
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
February 9th 20055959
Cold joints: interaction with the factory
Modification of bolts position and number
We asked non-magnetic seal
February 9th 20056262
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
February 9th 20056464
Neutron measurements Neutron measurements statusstatus
44
Device Location Beam type Average Beam int.
(mA)
Thermal n flux
(cm- 2 s- 1)
Non thermal n flux
(cm- 2 s- 1) NaI 1 Positive 1.5 3.5 – 4 unknown Pisa LiI + Bonner 2 Positive 1.67 6 ~ 25 He3 1-2 Positive 1.5 6- 7 unknown Tokyo
He3+ Bonner 4 Positive 1.8 2 ~ 12