Development of a table top TW laser accelerator for medical imaging isotope production

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Oswin Caldwell
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1 Development of a table top TW laser accelerator for medical imaging isotope production R U I Z, A L E X A N D R O 1 ; L E R A, R O B E R T O 1 ; T O R R E S - P E I R Ó, S A LVA D O R 1 ; B E L L I D O, PA B L O 2, 3 ; S E I M E T Z, M I C H A E L 2 1. P R O T O N L A S E R A P P L I C AT I O N S S. L, S A L A M A N C A, S PA I N 2. I N S T I T U T O D E I N S T R U M E N TA C I Ó N PA R A I M A G E N M O L E C U L A R ( I 3 M ), C S I C / U N I V E R S I D A D P O L I T É C N I C A D E VA L E N C I A / C I E M AT VA L E N C I A, S PA I N 3. C E N T R O D E L Á S E R E S P U L S A D O S U LT R A I N T E N S O S ( C L P U ), S A L A M A N C A, S PA I N

2 Motivation Radioisotope production for medical applications. Positron Emission Tomography (PET). Functional imaging. Needs a proton source for radioisotope production.

3 Proton acceleration for radioisotope production Proton acceleration with a cyclotron Protons over 10 MeV Radio isotopes: Carbon-11, Nitrogen-13, Oxygen-15, Fluorine-18, etc. Medication synthesis. Administration to subject for PET imaging.

4 Laser-driven particle acceleration. Solid targets, typically Al. Thin foils hundredths of nm few um. Laser intensity at target >10 18 W/cm 2. Interaction in vacuum (10-5 mbar). Wide proton energy distribution. Compact TW-class laser system fs J.

5 Chirped pulse amplification (CPA)

6 CPA systems Commercially available. Specifications enough for proton acceleration. 10 Hz repetition rate. Enough for proof of concept proton acceleration. We need higher repetition rate TW systems for practical applications in radioisotope production.

7 Challenges for higher repetition rate CPA Pump lasers: Pump lasers for Ti:Sapphire (Frequency doubled Nd:YAG, Nd:YLF) Change from flash lamps to diode pumping. Nd:YLF shows less thermal lensing effects. Distribute thermal loads into various beamlines. Flash-lamp DPSS

8 Antxeneta DPSS laser head

9 Olser pumps Amplifier Amplifier KTP (Frequency doubler) Amplifier Amplifier Oscillator 2 x up to 500 mj 532 nm 10 ns Dichroic mirror

10 Challenges for higher repetition rate CPA Ti:Sapphire amplifiers: Ti:Sapphire thermal lensing. Split thermal load into various amplifiers. Pre-compensate thermal lens by diverging seed beam. Cryogenic cooling.

11 Criogenic cooling of Ti:Sapphire dn/dt becomes smaller by a factor of two with cryogenic cooling. This is the best way to minimize thermal effects for high average power pumping. P. A. Popov, et al. (2011). Functional Materials, 18(4), Defranzo, A. C., & Pazol, B. G. (1993). Applied Optics, 32(13),

12 Our CPA system front end: E=1,5 mj f=100 Hz pulse=100 ps Input seed into the multi-pass amplification stages

13 Multi-pass amplification stages Two 3-pass amplification stages. 8 and 16 mm Ti:Sapphire crystals. Water cooled. 1st stage 100 mj pumping. 2nd stage 750 mj pumping. Telescopes to pre-compensate thermal lens. Convex mirrors in the amplifier for further compensation.

14 Output characteristics of the system E=93 mj after compression. t=43.2 fs. 2.1 TW Dx=8.2 mm. Dy=7.7 mm. Pulse duration Output beam profile

15 Compression and interaction chambers

16 Target positioning

17 Focal spot W/cm 2 2, , FWHM (x)=9 um FWHM(y)=5 um

18 Diagnostics Time of Flight detector: Interaction chamber Scintillation detector Flight tube ( ~ 2,3 m) Plastic Scintillator Optical fibers PMT

19 Diagnostics CR39 chips: Response calibrated in a conventional accelerator. Calibration curve relates proton energy with track diameter.

20 Diagnostics Thomson parabola 46 mm

21 Results Proton acceleration: 416 kev - 11,33 mm 367 kev 13,02 mm 315 kev 14,71 mm 276 kev 16,41 mm 237 kev 18,10 mm

22 Results Proton spectra:

23 System upgrade Drive pump lasers for the second multi-pass amplifier up to 500 mj per beam (total pump energy 2 J). Adjust beam sizes of pump and seed to maintain fluences. Implementation of cryogenic cooling.

24 Summary We have implemented a working TW laser system at a repetition rate of 100 Hz. Telescopes and convex mirrors in the multi-pass amplification stages pre-compensate the termal lens effects. Our laser is capable of accelerating protons up to 1 MeV in the current state. Work in an energy upgrade is in progress to reach 10 TW at 100 Hz using cryogenic cooling in the last amplification stage.

25 Thanks for your attention

Ultrafast Radiation Chemistry and the Development of Laser Based Electron Sources*

Ultrafast Radiation Chemistry and the Development of Laser Based Electron Sources* Robert A. Crowell Chemistry Division Argonne National Laboratory International Conference on Transient Chemical Structures