Mechanical and fluidic integration of scintillating microfluidic channels into detector system 1 Davy Brouzet 10 th September 2014

Context of the project Scintillator: Material that produces photons when exposed to particle radiations Used in particle accelerators to detect protons One of the biggest problem: Radiation damage in the scintillator due to radiations  Need to replace periodically the detectors in the LHC Liquid scintillators could be pumped in order to replace the damaged fluid  Combine liquid scintillators with the microfluidic technology to create reliable detectors Project’s aim: Design the pumping system and go further in the development of the detectors 2

Detector’s technology 3 Principle of the particle detector Typical microfluidic microchannels used for experiments

Guideline I. Characterization of the radiation damage of the liquid scintillator II. Development of the pumping system III. Temperature dependence of the scintillation efficiency IV. Pumping applied to microchannels 4

Radioactivity basics and energy loss through matter Particle radiation lose energy principally by electron excitation and ionization Two main radioactivity quantities:  Absorbed dose: Quantity of radiation energy absorbed by a material  Dose rate: Absorbed dose per unit time Energy losses strongly depend on particle and initial energy 5  Coding of a software that integrates the energy loss over the material’s depth

Radiation damage state of the art 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 LHC tunnel 6

Radiation damage experiment To determine the flow rate, one must know the maximum absorbed dose possible by the scintillator  Characterize the scintillation efficiency Tunnel closed at least until November  Make research and develop a possible design 7 De-activation of the exposed elements Scintillation 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

Container Design Very tight regulation constraint to expose a liquid to radiations  Best to keep the scintillator in a closed reservoir 8

Material’s choice for the container Main body: Epoxy resin or Aluminium Optical window: Borosilicate glass or more radiation resistant materials such as Quartz or transparent epoxy resins Tightness: O-rings not adapted, better to use glu epoxy resin 9

Pumping system flow rate estimation 10

Pumping system For HEP experiments or higher dose rate applications, such as hadrotherapy : Positive displacement pump 11

Pumping system 12 For MicroScint experiments: Syringe pump Large flow rate range and pressure up to 2.2 bars Glass syringe and materials chosen for chemical compatibility

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 luminosity  See if any dependence with the EJ-305 liquid scintillator 13

Design of the temperature experiment Materials selected for their chemical compatibility with the scintillator 14

Temperature dependence results Clear temperature dependence for the EJ-305 scintillator, good concordance with literature Best to avoid heating or calibrations should be done to correct the measurements  Need to determine the heating in applications 15

Photobleaching effect Liquid scintillators composed of wavelength shifters to better measure the output light with Photomultiplier Tubes Photobleaching used to damage the scintillator and to simulate the effect of radiation 16

Pumping applied to microchannels 1. Replacement with fresh scintillator  Validity of the technique proved! 17

Pumping applied to microchannels 1. o 2. Luminosity/Flow rate dependence  The higher the flow rate, the lower the damage and the higher the luminosity 18

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 19

Pumping applied to microchannels Main differences of the photobleaching experiments with respect to radiation damage:  Probable threshold value for the radiation damage  To avoid any flow rate dependence or any luminosity difference between the microchannels, possibility to have a flow rate high enough to avoid measurable radiation damage  General behaviour still holds for the several applications 20

Conclusion Research done for a radiation experiment in the LHC tunnel and development of a first set of solutions Pumping system designed for experiments and various possibilities for an application system depending on the flow rate and other characteristics needed The photobleaching effect allowed us to prove the validity of the pumping in microchannels and to investigate the behaviour of the scintillating liquid in various cases Temperature changes will affect the scintillation efficiency. One must quantify this change to find the best solution Oral self evaluation Acknowledgments 21

Thank you for your attention, Any question is welcomed! 22