M.Moll, M.Glaser, C.Joram

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RADMON Technical meeting 22.July 2004
Passive Dosimeters for the LHC Experiments

• M.Moll, M.Glaser, C.Joram
• CERN PH TA1 SD
• (http//cern.ch/ssd)
• F.RavottiCERN TS -LEA

I have 4 more transparencies

• Why is PH-TA1-SD involved?
• Organization of working group (as of 4/2004)
• Workplan (as of 4/2004)
• Aim of todays meeting

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Why is PH-TA1-SD involved?
April 2004

• PH-TA1-SD proposes to work on the evaluation and
  development of passive and active radiation
  monitors in collaboration with the LHC
  experiments with theMotivation to (1)
  Continue and extend dosimeter developments for
  the IRRAD facilities to serve all LHC
  experiments. (2) Keep the Student Federico
  Ravotti attached to our group
• Deal The LHC experiments provide financing
  for a doctoral student and TS-LEA the quota
  PH-TA1-SD invests manpower into the project
  (M.Moll and M.Glaser)
• Federico Ravotti is doctoral student in TS-LEA
  (attached to our section) since July 2004

July 2004
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Organization of the working group(Transparency
from April Meeting just filled in some names)

• PH-TA1-SD (M.Moll, M.Glaser, F.Ravotti)
  external collaborators together with the
  Experiments
• Design, develop and provide dosimeters and
  dosimeter module(s)
• Coordination of the common efforts within the
  dosimeter group
• Design of front-end electronics (if OSL needed)
• Design of basic prototype readout card with
  standardized output signals
• LHC Experiments
• Clarification of the specific requirements of the
  Experiment
• Integration into the Experiment (space, mounting,
  cabling, power supply,..)
• Experiment specific detector control interface
• Provide one responsible for these activities

Alice Marc Tavlet (CERN) ATLAS Marko Mikuz
(Ljubljana) and Per Grafstroem (CERN) CMS
Alick MacPherson (CERN) LHCb Doris Eckstein
(CERN)
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A possible work plan(Transparency from April
meeting)

• 6/2004 Specification of requirements
• Each LHC Experiment documents about its specific
  requirements
• Written agreement between Experiments and
  dosimeter working group specifying
• responsibilities
• work plan and milestones.

• A work plan could then look like
• End of 2004
• First prototype of an integrated board tested
• First prototype of basic readout system ready
• Integration into experiments clarified
  (positions, cabling, signal type)
• Middle of 2005
• Components for the radiation monitoring boards
  fixed
• End of 2005
• Prototypes of integrated boards with full readout
  electronics tested
• Series production ready to start
• Beginning 2006
• First boards ready (Is this too late?)
• 2006 Series of radiation tests of full dosimeter
  boards (final calibration)

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Aim of today's meeting
The aim of the meeting is to understand which and
how many passive dosimeters will be needed by the
LHC experiments in order to possibly launch a
common purchase of dosimeters respectively a
common activity leading to the set-up of the
required infrastructure to read them.

• Update on our activities (PH-TA1-SD) ? Maurice
  Glaser
• Which kind of passive dosimeters are used at CERN
  ?Which infrastructure is available? ? Alanine
  (Helmut Vincke, CS-RP) ? RPLs (Helmut
  Vincke, CS-RP) ? TLDs (Marco Silari, Jacques
  Wolf, CS-RP)
• Reports of the LHC experiments radiation
  monitoring contact persons
• Discussion on - type of dosimeters -
  number of needed dosimeters
• Next meeting Deadline for providing ourselves
  with some more detailed information about
  a) interest to join a common activity on passive
  dosimeters b) type and number of dosimeters
  needed

Thank you!
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. towards LHC
Rough estimate of doses/year
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Spare Transparencies

• Some transparencies shown in April 2004

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Radiation Monitoring Technologies- Active
devices -
most of the active devices can be used as
passive dosimeters . just to remind you
Devices and their flexibility

• RADFETs
• different gate oxide thicknesses
  (change of sensitivity)
• different gate voltages
  (change of sensitivity)
• different producers, different packaging (change
  of response, fading)
• OSLs - Optical Stimulated Luminescence
• doping of the substrate
• Standard devices (pure OSLs) sensitive to
  ionizing radiation
• Boron doping increased sensitivity to thermal
  neutrons
• Mixing with Polyethylene increased sensitivity
  to fast neutrons
• Reverse biased Pin diodes
• Equivalent principle to the Inner Silicon Tracker
  detectors
• different size and thickness, epitaxial detectors
• different doping levels, oxygenated
• Forward biased Pin (photo) diodes
• commercial devices little flexibility
• New Semi-commercial source (see presentation of
  Maurice)

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Radiation Monitoring Technologies- Some passive
devices -

• Polymer-Alanine dosimeters (PADs)
• Irradiation breaks up bonds and forms free
  radicals
• EPR can quantify the number of free spins
• Radiophotoluminescent glass dosimeters (RPLs)
• Ionization charges color centers
• UV light excitation releases visible light
• Thermoluminescence dosimeters (TLDs)
• Emission of light when the material is heated
  after irradiation
• Can be reused after reading (heating)
• 7LiF for ionizing radiation
• 6LiF for ionizing radiation and neutrons (n,a)
  capture
• Hydrogen Pressure Dosimeters (HPDs)
• Polyethylene in a sealed quartz container
• Disintegration of the polyethylene by irradiation
  releases hydrogen
• Hydrogen gas pressure is proportional to the
  received dose
• LiF Crystals
• Formation of color centers increases light
  absorption
• Activation foils
• Nuclear reaction form radioactive isotopes

Figure I.Floret (TIS/RP)
Note CERN has a High-Level Dosimetry group in
SC(TIS)/RP (H.Vincke, I.Brunner et al.)!
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Passive Dosimeters
TLD LiF crystal PAD (Alanine) Dye films RPL HPD
Dose Range 10 mGy to 100 Gy 1KGy to 100MGy 10Gy to 1MGy 1-250Gy10KGy-1MGy 100mGy to 1MGy 10 KGy to 10MGy
Readouttechnique Heating Light emission Light absorption EPR Densitometer UV (365nm) Light emission Pressure measurement
Comment standard device Thermal neutron measurement Very small
Data I.Floret (SC/RP High level dosimetry)
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Ionization (DOSE) Ionization (DOSE) Displacement in Silicon (Particle Fluence) Displacement in Silicon (Particle Fluence) Instantaneous Dose Rate
RADFET OSL Photo-diode Pin-diode Pin-diode
integrating integrating, erased by readout integrating integrating instantaneous current
Operation unbiased dark unbiased 100V (reverse) 100V (reverse)
Read-out IDS10-200mA (5s) IR 800-1500nm 1mA (forward, 200 ms) 100V (reverse) 100V (reverse)
Signal VDS 1-20V Light 500-700nm Forward bias Leakage current Induced current
Range 10mGy-10KGy 10mGy 100Gy 1012-1015 cm-2 1011-1014cm-2
Sensitivity 1-100 mV/GyDecreasing with integrated dose depending on photo sensor 150mV / 1012 n/cm2 1mA / 1012 n/cm2 1nA / 50mGy/s
Positive has already been used in HEP erasable, sensitivity does not decrease, can be adopted to measure fast and thermal neutrons, used in satellites COTS, very low cost has already been used in HEP, high sensitivity in low fluence range has already been used in HEP beamdump trigger (BCM activities)
Negative signal needs T correction, non-linearity New technology in HEP, needs development Annealing not well charact., signal needs T correction annealing difficult to simulate, signal needs T correction - background current increasing with lifetime (irradiation)
Costs for one mounted device 140 CHF 200 (non commercial) 2 150 (??)(non commercial) 150 (??)(non commercial)
Fluence to Dose (MIP) 2.666x10-10 Gy cm2
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Our Mandate
Our mandate

• Develop and characterize dosimeter boards with
  on-line readout for and together
  with the LHC experiments
• Boards being as flexible as possible
  (dose/fluence range, sensitivity, particle type,
  shape of board ) in order to allow and optimal
  adoption to specific sub-detector environments.
• Output signal compatible to all Detector Control
  Systems
• Provide the dosimeter boards and/or active
  dosimeters to the experiments
• Support the experiments in qualifying passive
  dosimeters

Not our mandate

• Impose our radiation monitoring concepts on the
  experiments
• Integrate the dosimeters / dosimeter boards into
  the experiments

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Towards a workplan (1/2). some questions to be
discussed

• Measurement for which purpose?
• (Beam dump? ? Beam Condition Monitor Group)
• Detector protection (e.g. switching off a
  sub-detector) ?
• Test of radiation shielding?
• Long term monitoring?
• Analysis of beam accidents?
• Instantaneous dose rate measurement needed ?
• trigger on too high dose rate/flux needed? if
  so, in which time scale?
• Measure which kind of information?
• ionizing dose
• displacement damage
• thermal neutrons
• Dose/Fluence range and sensitivity needed?
• Active and/or passive devices ?
• readout cycle? / replacement cycle?

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Towards a workplan (2/2) some questions to be
discussed

• Number of monitoring modules?
• Environment of module?
• Temperature and Temperature stability?
• Space constrains?
• Maximum size of sensor module?
• Distance between sensor and readout electronics
  (cable length)?
• Lifetime of modules?
• Will we be able to repair/replace/upgrade them?
• Readout
• Radiation hard electronics on-board needed (OSL
  needed)?
• Specific restrictions due to the individual
  experiments?
• Which kind of signals can be accepted by the
  detector control system of the Experiment?
• Deadlines
• Decision about size of the module
• Decision about number of cables
• Decision about signal type
• Installation deadline
• Service/Maintenance after installation
• Which kind of service/maintenance is expected
  after installation?