PSI 27/6/2006

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PSI 27/6/2006 C.Bemporad
THE TAMING OF MEG News on Calibration Methods
Cockcroft-Walton Accelerator ?-sources on
wire ?-lines from neutron capture on Ni ?-decay
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THE MEG EXPERIMENT COCKCROFT-WALTON
ACCELERATOR PROTON BEAM-LINE
DELIVERY OF THE COCKCROFT-WALTON
ACCELERATOR DEFINITION OF THE PROTON BEAM
LINE BELLOWS SYSTEM FOR THE TARGET INSERTION
INTO COBRA REQUEST FOR SPACE BEHIND THE MEG
AREA FINANCING ETC.
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POINTS TO BE CONSIDERED

• The C-W accelerator is delivered on June-July
  2007, after the
• start of the MEG data taking
• The installation of the C-W accelerator at PSI
  and the C-W tuning
• requires at least one month
• The C-W accelerator installation should not
  interfere with the MEG
• running
• From time to time, some interventions and
  repairs on the C-W will
• be needed
• The mutual effects between the C-W accelerator
  and the COBRA
• magnet must be small. Keep an adequate
  distance between them.
• A large amount of space is needed (and
  available) in the MEG area for the
• bellows system and for the p-beam optical
  elements
• It is convenient that the turning on and the
  tuning of the C-W accelerator
• take place while the MEG experiment is in
  normal running

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CONSEQUENCES

• Need for space at the back of the MEG area for
  the accelerator installation
• Radiation Safety independently surveyed area
• Bellows system for p-beam and Li target
  introduction into COBRA
• p-beam opposite to the ?-beam and on the same
  line (simpler !)
• C-W accelerator at ? 7 m from the COBRA centre
• Optical elements needed for beam focusing and
  centring
• (4 steering magnets, 2 quadrupoles)
• The C-W accelerator construction and the bellows
  system preparation depend on a decision on the
  availability of the space downstream of the MEG
  area
• A RATHER COMPLEX PROJECT ! 1) MEG collaborative
  work 2) Help from the National
  Laboratories of Legnaro (advice and spare items)
  (Letter to/from and from the Lab. Director
  G.Puglierin)

RELIABLE AND EASY CALIBRATIONS ARE ESSENTIAL TO
MEG An earlier C-W installation translates into a
saving in time, in effort, in money (The
experiment can be tuned when the PSI beam is not
allocated to MEG and during machine-off periods)
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PROBLEMS WE ARE IMMEDIATELY FACING URGENT
SOLUTION NEEDED !
C-W accelerator in the engineering phase. Some
characteristics depend on the accelerator
position and hall space availability. Wait for a
decision........? Delayed delivery ! The order
and the construction of the bellows system depend
on the C-W position. The cost of the bellows
system is approx. 85.000 euro If immediately
ordered, it could be ready by November
2006. Desirable a BVR positive recommendation
about the use of hall space for the C-W
installation during this June 27th meeting.
Present INFN financial difficulties. Decision
on our requests (To be based on hall space
availability !) during the July 3rd, or
successive Commission 1 September meeting
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Cockroft-Walton Accelerator in a fixed
position and Bellows system for inserting the
p-beam and the LiF target into COBRA
P-beam and target inserted into COBRA
(not to scale)
P-Beam and target out of COBRA
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THE PRESENT MEG AREA The Bellows System and the
p-beam optics (4 steering magnets and 1
quadrupole doublet) can be arranged in the MEG
area
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Present position of the shielding walls behind
the MEG area
MEG AREA
AREA ON THE BACK OF MEG
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Proposed position of the new shielding
walls Behind the MEG area
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Possibility of bellows system, beam optics, C-W
accelerator installation in a single MEG area
(not advisable.......)
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SINGLETRON COCKCROFT-WALTON ACCELERATOR
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BELLOWS SYSTEM FOR THE INTRODUCTION OF THE PROTON
BEAM AND OF THE LiF TARGET INTO COBRA

• The bellows system project is ready
• (the beam section from the accelerator to the
  bellows system must be completed)
• It is advisable that the bellows system be built
  during the summer 2006,
• be fully tested under vacuum and be tuned
  before the end of the year
• Development of the safety system and of the
  computer controls
• Improvements in the LiF target and holder.
  Cooling. Beam centring and
• beam current readings. Beam optics controls
• Avoid, if possibile, a time-overlap between the
  installation of the bellows system
• and the delivery, mounting, tuning of the C-W
  accelerator
• ESTIMATED COST OF THE BELLOWS SYSTEM ? 85 Keuro
• (if the beam optics elements and power supplies
  are all available at no cost)

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microphoto of LiF TARGET
very small p-beam irradiation cells of approx.
30 ?m
intermediate p-beam irradiation
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heavy irradiation at p-beam spot
IMPROVE Lithium Fluoride TARGETS BETTER CARE OF
TARGET COOLING AND GOLD PROTECTION
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?-sources on wire recent improvements
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Polonium Wire-Sources RINGS IN LIQUID XENON PMT
Q.E. Measurements
Now in print on Nuclear Instruments Methods
Great if used in the bulk of any Liquid Detector
!
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Quantum efficiency determinations in Large
Prototype
CHECK OF PMT PROPERTIES IN THE FINAL
CALORIMETER DURING THE EXPERIMENT Americium WIRE
SOURCES 5 WIRES, 5 DOT-SOURCES PER WIRE
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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first SORAD/ISOTOPE PRODUCTS AMERICIUM
WIRE-SOURCES made by a thermocompression method
Irregular rings, well simulated by the Monte
Carlo Method !
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EXTRA RD BY SORAD New modified sources
shipped to Pisa on June 18th Elimination of the
wing and of its shadow
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EXTRA RD BY SORAD interesting new
method Thermocompression of an Am-source strip
wound around the wire
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thermal neutron capture on nickel and 9 MeV
?-line
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Calorimeter monitoring by NEUTRONS AND
NICKEL-LINE (Americium Source) hourly
calibration
large-prototype
NaI
NaI ?/E2.5
PROBLEM in the LXe the line is worse larger
background due to fast neutron reactions n2n,
n1?, n2?, n3?, ..
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• WAY-OFF
• reduce the neutron energy by use of a
  Californium source
• better reject ?-particles from sources on wire
• select thermal neutrons events by a delayed gate
  window
• (? 100 ?s) and a trigger from fission prompt
  ?s (lower rate)
• A GENERATOR OF 9 MEV ?s FROM NICKEL
• MUST BE READY IN TIME FOR THE FIRST MEG RUN
• present problems with status of large Sodium
  Iodide Detector

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hydrogen target to be used inside COBRA (new
test JUST NOW in Pisa !)
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THE TAMING OF MEG
all proposed calibration methods were tested and
most of them are up to expectations WE ARE
READY..