1

Mechanical and fluidic integration of scintillating microfluidic channels into

detector system

Davy Brouzet 10th September 2014

2

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

3

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

4

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

5

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

6

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

7

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

8

II. Pumping applied to microchannels1. Replacement with fresh scintillator

Validity of the technique proved!

9

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

10

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

11

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?

12

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

13

III. Pumping system for applicationFor HEP experiments or higher dose rate applications, such as

hadrotherapy : Positive displacement pump

14

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

15

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

16

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

17

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

18

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

19

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

20

Thank you for your attention,

Any question is welcomed!

21

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