CERN scintillating microfluidics channels Hadrotherapy Liquid scintillators Radiation damage Microfluidic technology 1 Davy Brouzet 3 rd March 2014

I-Radiation and damage II-Temperature effect III-Fluidic consideration and pumping IV-Chemical compatibilities V-Cooling VI-Gantt diagram and objectives 2 CERN scintillating microfluidics channels

Radioactivity Theory Radio or hadrotherapy daily doses about 2Gy (2min duration 1 ) ATLAS: 100Gy/year dose When passing through matter, particles lose a certain amount in energy via ionization and molecule excitation to higher energy states. 3 1 proton-cancer-treatment.com Absorbed dose: J/kg Equivalent dose: Depends on the radiation type (for biological effect)

Radiation damage in scintillators Charged particles energy losses (at the ten MeV scale): 4 Excitation Ionization π-electrons Other electrons π-electrons Other electrons Fluorescence Thermal dissipation Slow scintillation (damage?) Damage (quenching) 2 consequences: Diminution of local scintillation and of attenuation length  Light output diminution Strongly depends on type: Solids  Damaged by low irradiation (50% decrease of light output for anthracene at 10kGy). Sometimes effects at Gy. Liquids  60% decrease in scintillation efficiency for BC-505 at 50kGy irradiation. Energy transfer (and distribution) depends on the nature of the particle (mass, charge and energy)  α -particle>protons>neutrons No significant effect of dose rate on radiation damage for the majority of solid and plastic scintillators Radiation damage of SU-8? Silicon? ≈5% of absorbed energy 2 ≈ 28% of absorbed energy ≈67% of absorbed energy 2 See Annex for details

Temperature effect In liquids scintillators, an increase in temperature will induce an higher viscosity and higher light output, especially at high temperatures. Maximum 6% gain for toluene solutions between 25°C and 5°C. Photomultipliers efficiency can also be increased by a lower temperature! No reasons that radiation damage should depend on temperature  Important to keep it below room temperature. Tests should be done on the specific scintillator used to quantify the radiation damage and the temperature effect. 5

Flow rate estimation 6 Irradiation limit assumed for liquid scintillators: 10 4 Gy * 2 See Annex for details

Microfluidic considerations cP viscosity taken for 1,2,4 trimethylbenzene (different values depending on source) 4 See Annex

Pumping technologies Positive displacement pumps are adapted to low flow applications Micropumps  Adapted to microfluidic application (not so high pressure difference for really small flow rates) 8

Chemical compatibilities Principal liquid scintillators made of xylene (EJ-301), pseudocumene (EJ-305) and ??? (EJ-309) Chemical compatibilities: Chemical compatibilities.pdfChemical compatibilities.pdf EJ-301 quite difficult to find adapted materials, especially for O-rings  FKM or FFKM elastomers. Not compatible with PEXIGLAS. EJ-305 is less toxic and can for example also be used with Viton. EJ-309 is made of a particular alkyl-benzene. Which one? However, the fact that it is sold with a ‘low chemical toxicity’’ characteristic indicates that it would be more adapted to a pumping use. Optical properties lower than for the EJ-305 (attenuation length divided by 3, higher refractive index, lower light output) In all the cases, a sealless pump would avoid leakage and thus toxic damages and problems in void conditions. 9

Cooling 10 5 Micro-channel cooling for HEP particle detectors and electronics

Planning and objectives See Gantt diagram for planning: Organisation\Gantt Diagram.pdfOrganisation\Gantt Diagram.pdf Objectives: 1. Finish bibliography review (oxygen quenching, cooling systems, chemical compatibility of EJ-309…) 2. Deeper investigation on heat exchanges 3. Viability of the system both in CERN and hadrotherapy application. 4. Start design of system (pump choice, mechanical integration, define final flow rate, determine if cooling system is needed and if yes which one) 5. (Numerical simulation?) 6. Fabrication of prototype 7. Tests on radiation damage (and temperature effect) on selected scintillator 11

Thank you for your attention 12

References 13

Annex 14

Annex 15

Questions Energy particle at CERN? Confirm the irradiation found in the CERN report and in Alessandro’s Thesis. How the total radiation is computed from the light intensity? Is there a calibration to be done? Probably best if the optical properties are the same in all the channels. Workshop budget? Name of expert for final presentation in September. Can we organize some meetings every month with Mr. Schiffmann? 16