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					LXe calibrations, PMT tests, cryostat
construction

1. Alpha sources on wires
2. 9 MeV  from neutron capture in Nickel
                                             Calibrations
3. 0


4. further calibration methods ?
5. PMTs tests
6. Cryostat status


                                                            1
                                       February 9th 2005
 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  )
                                              LP Front face Lateral face
• 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


                                                                           2
3
4
•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
                                          5
                      February 9th 2005
Small displacement of the two front wires



      LXe                  GXe




                                            6
PMT alpha direction




                      7
Charge vs Cos in LXe
           Front Face




    Data                MC


                             8
          LXe/MC

                   New PMTs

4 front
                   Old PMTs
sources




                              9
          LXe/MC


4 front
sources




          After applying QEs
                               10
 Towards the final calorimeter




70 kHz photons with E>5 MeV from muon radiative decay @ R()
       3x10**7. Total sources rate O(15 KBq @ 5 MeV)
                                                               11
Po half-life=138 days


              Trigger was
              changed several
              times …




                                12
            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 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 DETECTORS
                     unique feature !
                                                                                13
                                                            February 9th 2005
   SPECIFICATIONS FOR THE PRODUCTION OF SEVERAL
                 Am WIRE-SOURCES                             SPECITICATIONS
           AND SEVERAL Am DISK-SOURCES
                 January 5th 2005                            AND CONTRACT
The wire sources should be produced according to          FOR THE PRODUCTION
the 3 model drawings “final calorimeter” (15
wires), “large prototype” (8 wires), Pisa device (2     OF Am WIRE-SOURCES AND
wires).
                                                           OF Am DISK-SOURCES
Final calorimeter: 15 wires, 5 dot-sources per
wire,Large prototype: 10 wires, 2 dot-sources per
                                                          Ready: end of March 2005
wire, Pisa device: 2 wires, a single dot source         (TOTAL ACTIVITY < 40 kBq)
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
                                                               Each dot-source:
source mounting, should be < 200 m. The source       small radioative foil fixed on wire by
surface should be as smooth and regular as
possible. The dot sources should be covered by a             “thermocompression”
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        TESTED AT NITROGEN TEMPERATURE
linear dimension < 2 mm. The position of each dot       AT THE ENEA LAB. IN ROME. OK !
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)        NEEDED FROM PSI:
should be easily visible.
The wires must be shipped without damaging them;         •Authorization of nuclear security
each wire could perhaps be mounted on a thin              for products
plastic rod or wrapped around a large diameter
spool.                                                   •Authorization for import of
                                                          radioactive sources
The 25 disk-sources should be gold plated disks of
                                                         •Auhorization for production of
diameter 5 mm and have an activity of  500 Bq per
source. Each source should be covered by a                detectors using radioactive sources   14
protective gold layer  1.5 m.
                                                                       February 9th 2005
             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


Reference Mark                                                 Am dots

                 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
                                                                                   15
                                                               February 9th 2005
                 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
                  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
                                                                                         16
                                                                     February 9th 2005
                 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
                                                                                  17
                                                              February 9th 2005
                    18
February 9th 2005
   rather narrow
  energy-spectra

 possible mounting
     on special
supports and screws
                                          19
                      February 9th 2005
Will it be possible to use them @ beam on?

                                                         20
                                     February 9th 2005
   2) 9 MeV gamma line from neutron capture on
           Nickel:Experimental 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.



                                                      21
                                  February 9th 2005
γ-line from n-capture on Ni, I, Al, H2;
natural radioactivity Tl, K; Am/Be source
K            H2        Am/Be                      Ni
1.46 MeV     2.2 MeV 4.4 MeV &               8.54 MeV &
                       1st escape            1st escape
                 Tl                   I
                 2.6 MeV          6.8 Mev
                                           Al          Ni
                                        7.7 MeV     9 MeV




           Black: Am/Be source and 1 cm Ni
           Red: no Am/Be source
           Green: no Am-Be source, no Ni
           (Gotta Beam on)



                                                                              22
                                                          February 9th 2005
 THERMAL NEUTRON CAPTURE ON NICKEL                                  neutron generator (Pavia ?)

                            D + H  He + n Q = 3.27 MeV
                                         2         3
Potentialities :
                            D + 3H  4He + n Q = 17.59 MeV
• 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 γ-line

  Open problems:
  • monitoring from calorimeter back
  • only at one location ?
  • some dispersed neutrons and radioactivity                                       NaI 20 x 20 x 36 cm3
  • test of the method at high beam intensity
  • useful test with the “large prototype”
    (already foreseen in April, with Am/Be source)
       • Intensities from 106 n/s to 108 n/s                                          Polyethylene
       • Typical pulse rate and pulse width 10 Hz and 1 μs
       • Time separation of direct from delayed reactions                              0.25 cm Nickel plate

       • Single pulse mode                                                                               23
                                                             3 cm 20 cm   February 9th 2005
           Possibilities
POLY                    POLY     POLY     POLY       POLY




          NaI


                                                            n




       Am/Be


                0.25 cm Nickel 3 cm polyethylene            24
                                        February 9th 2005
                                           How often can it be
3)   0   calibration…                     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 -/sec
                                         Target
                                            • Collimate:   2PMTs x 2PMTs ~ 150cm2
                                   up
                                                        (1 position)
                 0
                                            • 2 /sec
                                   down
                                            • # of PMTs on incident face: 216
                                           PMTs (54 positions)

                      target                • required: 30,000 evts/position
                                            • takes 30,000 x 54 / 2 =

                                                        810,000sec~    10 days
                                                                                  25
                                                              February 9th 2005
                   3) Further calibration methods...
        500 KV PROTON ACCELERATOAND LITIUM TARGET FOR A
                        17.6 MEV GAMMA LINE
       7Li   (p,)48Be         [P.R. 73, 666 (1948), N.P. 21 1 (1960), Zeitschrift f. Physik A351 229 (1995)]
   3
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 ?
                                                                                                            26
                                                                         February 9th 2005
Previously used...




                                         27
                     February 9th 2005
     7Li   (p,)48Be
 3

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 12”x12”     spectrum




                                           Crystal Ball Data

                                      0
                                 1



                                                                28
                                            February 9th 2005
A further interesting possibility...   Cecil et al. NP A539 75 (1992)
                                           10x10 cm NaI crystal
         11B   (p,)612C
     5

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 !!



                                                                        29
                                                    February 9th 2005
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...
                                                                              30
                                                       February 9th 2005
Cal. calibration from the target position, monitoring at the cal. back




                                                                 rails


                                               cockroft




                                              focusing elements
  at the cal. back the proton motion in the   (magnetic or electrostatic ?)
       COBRA field must be be studied
                                                                              31
                                                     February 9th 2005
        proton MC trajectories
          Ep 440 keV  28 MeV/c !!




Y(cm)                       the protons are not
                            reflected back by the
                            varying magnetic field

                            Θ ~ 8  giroradius < 12 cm


                            X(cm)



            Z(cm)                                          32
                                       February 9th 2005
                          Plane Z = 0 cm

Y(cm)
                                   ρ ~0.8cm




  X(cm)           Θ ~ 0.5  giroradius < 1 cm
          Z(cm)

                                                 33
                             February 9th 2005
                     KEEP MEG UNDER CONTROL
PARTICULARLY AT HIGH (AND VARIABLE) BEAM INTENSITIES.........

      BR   e  ~10-13                Beam Intensity~5 107 /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
                                                                       34
                                                   February 9th 2005
                5) PMT tests

       PMT in LP, LED pulsed (@ 1 khz)

 F18, TB type                     F0, 6041 (old)

<Q> = 50 pC                          <Q> = 87 pC




                                                             35
                                         February 9th 2005
              10 Khz
      TB                6041

<Q> = 50 pC            <Q> = 87 pC



                          photocathode
                        saturation effect




                                              36
                          February 9th 2005
              50 Khz
      TB                6041


<Q> = 50 pC            <Q> = 87 pC



                          photocathode
                        saturation effect




                                              37
                          February 9th 2005
               100 Khz
      TB                   6041


<Q> = 50 pC               <Q> = 87 pC


     Gain non linearity




                                                 38
                             February 9th 2005
            6041




t = 115 s




Anode current should be < 0.5 A


                                                       39
                                   February 9th 2005
                    TB




Lower photocathode resistivity (ZA much better)

                                                            40
                                        February 9th 2005
Zener Diodes on PMT Base




                                         41
                     February 9th 2005
       Linearity much improved




                       presently installed

T=-108ºC



              PMT with Zener




                                             42
          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




                                       43
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.

                                        44
             Results: FairChild


 68+75        5 Hz


 75+75       200 Hz


(75//75)x2    3 Hz


                                  45
       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

                                                                     46
                                                 February 9th 2005
Low pass filter in PMT base @ 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
     PMT+BGO
     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.

                                                                       47
                                                   February 9th 2005
  PMT Test using the base with Low Pass filter




Type Z                   Type ZR




                                                        48
                                    February 9th 2005
Chamber Set Up   Type Z

                                       Upper PMT temp.
                                          ~ - 85 °C



                            HV=800V for both PMTs
             Alpha source   Same interstage volt.,
             LED            same current between 2 PMTs

                 Type ZR

     Gas
                                        Lower PMT temp.
     xenon                                 ~ - 100 °C




                                                             49
                                         February 9th 2005
Oscilloscope Snapshot
                                                       Noise from Zener
       Type Z




  No noise was observed!!                                          Alpha event

       Type ZR




           Yasuko HISAMATSU MEG Collaboration Meeting Feb. 2005                50
                                                           February 9th 2005
     If the base Type ZR doesn’t work…
 We have an alternative; active base with MOS-FET
     Adopted in the πβ experiment
     MOS-FET is operational in 165K




                                                                  51
                                              February 9th 2005
        When a solution is found


Start testing PMTs: 300-400 at Pisa
(Cryo facility) and 600-700 at PSI (LP)




                                                              52
                                          February 9th 2005
    6) Cryostat: designs ready; tenders
    and procurements organization
Tenders have been organized in three parts:
1. Conventional part
2. Cold and warm windows
3. 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.
                                                                          53
                                                     February 9th 2005
         SIMIC profile in cryogenics application




http://www.simic.it/eng/home.htm

                                                                 54
                                             February 9th 2005
             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)


                                                                      55
                                                 February 9th 2005
                                                                    FEA studies are in progress
                                                                                                                                           200000000

                                                                                                                                           180000000

                                                                                                                                           160000000

                                                                                                                                           140000000




                                                                                                                    max principal ( Pa )
                                                                                                                                           120000000

                                                                                                                                           100000000

                                                                                                                                           80000000

                                                                                                                                           60000000

                                                                                                                                           40000000

                                                                                                                                           20000000

                                                                                                                                                  0
                                                                                                                                                       0,0003          0,0004                      0,0006            0,001
                                                                                                                                                                                 thickness ( m )

                                                                                                                                                                cerniera max princ-thickness       membrane theory



                                                                                                                                           200000000
                         0,0005

                                                                                                                                           180000000
                        0,00045

                                                                                                                                           160000000
                         0,0004

                        0,00035                                                                                                            140000000
max displacement ( m)




                                                                                                                    max principal ( Pa )




                         0,0003                                                                                                            120000000

                        0,00025                                                                                                            100000000

                         0,0002                                                                                                            80000000

                        0,00015
                                                                                                                                           60000000

                         0,0001
                                                                                                                                           40000000
                        0,00005
                                                                                                                                           20000000
                             0
                                  0,0003                0,0004                     0,0006                   0,001                                 0
                                                                 thickness ( m )                                                                       0,0003          0,0004
                                                                                                                                                                                 thickness ( m )
                                                                                                                                                                                                   0,0006            0,001
                                                                                                                                                                                                                             56
                                           incastro max displ-thickness      cerniera max displ-thickness
                                                                                                                                                                         February 9th 2005
                                                                                                                                                                                   membrane theory
                                                                                                                                                                Incastro max princ-thickness
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




               This area is reinforced   Internal welded foil .3 mm or less welded on external
                                         Frame necessary to test the window prior the final welding
 Bolted area
                                         on the cryostat body.                                     57
                                                                     February 9th 2005
 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
                                                                         58
                                               February 9th 2005
Cold joints: interaction with the factory

     Modification of bolts position and number


                     We asked non-magnetic seal




                                                    59
                                February 9th 2005
                  Pisa 30-December-2004
Cold joints




                                          60
              February 9th 2005
PMTs supporting structure design




                                              61
                          February 9th 2005
            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                                                         62
                                                         February 9th 2005
2005




       Calorimeter
       schedule




                                  63
              February 9th 2005
Neutron measurements status

           Device      Location   Beam type       Average    Thermal n    Non thermal
                                                 Beam int.      flux         n flux
                                                   (mA)      (cm-2 s-1)    (cm-2 s-1)
Pisa    NaI               1       Positive           1.5      3.5 – 4       unknown
        LiI + Bonner      2       Positive          1.67         6            ~ 25
Tokyo   He3              1-2      Positive           1.5        6-7         unknown
        He3+ Bonner       4       Positive           1.8         2            ~ 12




                                             4




                                                                                        64
                                                                    February 9th 2005