mechanical and fluidic integration of scintillating microfluidic channels into detector system 1...
TRANSCRIPT
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Mechanical and fluidic integration of scintillating microfluidic channels into
detector system
Davy Brouzet 10th September 2014
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Presentation guidelineI. Context and primary information
II. Pumping system for experiments and application to microchannels
III. Pumping for future applications
IV. Radiation damage characterization
V. Temperature dependence of the scintillation efficiency
VI. Conclusion
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I. Context of the project Large Hadron Collider used for
high energy particle experiments at CERN
Engineering Office in the Detector Technologies section takes part in the development of new detectors
Solid scintillators are the main material of several detectors. They produces photons when exposed to particle radiations
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I. Scintillation process in liquids and photobleaching effect
Another cause of light output decrease: Radiation damage in the scintillator due to radiations Need to replace periodically the detectors in the LHC
Photobleaching effect: Decreases the light output
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I. Scintillating microfluidic detector’s technology
Principle of the particle detector
Typical microfluidic microchannels used for experiments
Liquid scintillators could be pumped in order to replace the damaged fluid
Combine liquid scintillators with the microfluidic technology to create reliable detectors
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I. Future applications1. Single particle tracking in HEP
experiments
Position detection of particles with double layer microchannels
2. Beam monitoring in hadrotherapy
High particle flux Quicker radiation damage
Project’s aim: Design the pumping system and go further in the development of the detectors
xEnergy distribution
Particle beam
x
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II. Pumping system for experiments
For MicroScint experiments: Syringe pump
Large flow rate range and pressure up to 2.2 bars
Glass syringe and materials chosen for chemical compatibility
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II. Pumping applied to microchannels1. Replacement with fresh scintillator
Validity of the technique proved!
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II. Pumping applied to microchannels
1. o
2. Light output/Flow rate dependence
The higher the flow rate , the lower the damage and the higher the light output
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II. Pumping applied to microchannels
1. D
2. D
3. Difference in light intensity between the channels
May have a difference of scintillation efficiency in the detector with continuous pumping
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II. Pumping applied to microchannels Main difference of the photobleaching experiments with
respect to radiation damage: Probable threshold value for the radiation damage
To avoid any flow rate dependence or any light output difference between the microchannels, possibility to have a flow rate high enough to avoid measurable radiation damage
Behaviour will depend on the type of pumping: continuous or periodic pumping
Next step: What are the requirements for a pumping system in hadrotherapy or HEP experiments?
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III. Pumping system flow rate estimation Taking 100x 200 microchannels and a threshold absorbed
rate of
The higher the dose rate the higher the differential pressure
1. For HEP experiments: for Periodical replacement sufficient
2. For hadrotherapy: for Continuous pumping might be an option
Pumping system with small differential pressure and flow rate
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III. Pumping system for applicationFor HEP experiments or higher dose rate applications, such as
hadrotherapy : Positive displacement pump
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III. Radiation damage state of the art Lack of information concerning the radiation damage!
Literature Efficiency decrease of solid scintillator detectors in ATLAS for dose
greater than 3 kGy Very complex phenomenon, strongly depends on particle type,
solvent, wave-shifters used and the parameters of the experiment Not possible to extract from the literature a value of the
maximum absorbed dose
First measurable damages should appear between 1 and 1’000 kGy
Plan some experiment to irradiate the scintillator in the irradiation facilities at CERN
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IV. Radiation damage experiment
Tunnel closed at least until November
Make research and develop a possible design
De-activation of the exposed elementsScintillation
measurement
Proton exposition
Avoid external contamination Container + Scintillator
Damage the scintillator but not the container
Excite the scintillator with electrons to quantify the scintillation process
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IV. Container Design Very tight regulation constraint to expose a liquid to
radiations Best to keep the scintillator in a closed reservoir Multiple discussions with the CERN Irradiation Facilities
department to find a design that fulfill all the requirements
Material choice to assure chemical and radiation compatibility
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V. Temperature dependence of the scintillation efficiency Temperature dependence of the scintillation efficiency: Up
to 100% difference between 80°C and 20°C Source of heating: electronic devices and radiation thermal
dissipation could decrease the light output See if any dependence with the EJ-305 liquid scintillator
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V. Temperature dependence results
Temperature dependence in the experiment Importance of the PMT temperature sensitivity of -0.4% per °C
?
Still those primary results tend to indicate a temperature dependence of the liquid scintillator
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VI. Conclusion Pumping system designed for MicroScint experiments
and validity of the replacement with fresh scintillator proved
Set of solutions for future application
Need to characterize the radiation damage: Contact with the irradiation facilities department and first design made to expose a liquid scintillator
Experiments tend to confirm the temperature dependence of the EJ-305
Oral self evaluation
Acknowledgments
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Thank you for your attention,
Any question is welcomed!
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III. Energy loss through matter Two main radioactivity quantities: Absorbed dose: Quantity of radiation energy absorbed by a
material. Units in J/kg = Gray (Gy) Dose rate: Absorbed dose per unit time.
Energy losses strongly depend on particle and initial energy
Coding of a software that integrates the energy loss over the material’s depth