ThomX, a Compton X-ray source project in Orsay

1. IN2P3 Les deux infinis Nicolas Delerue (LAL, CNRS) On behalf of the ThomX collaboration ThomX, a Compton X-ray source project in Orsay

2. The ThomX collaboration • ThomX is a collaboration between several French laboratories: • LAL (Orsay), HEP lab • SOLEIL, Synchrotron source • CELIA, Laser lab • C2RMF, archeology/museum lab • ESRF, Synchrotron source • NEEL, X-rays instrumentation • INSERM, medical research • Funding from “equipex”, IN2P3/CNRS, Université Paris-Sud XI, Région Ile de France,… • Full funding approved • Project leader: A.Variola, deputy: A.Loulergue Nicolas.Delerue@lal.in2p3.fr

3. The machine 50 MeV electrons Size ~10mx7m will be located in Orsay Optical resonator ~50MeV electrons X rays • Pixel det. ImXgam • From • ATLAS/CPPM • Photo gun S-band (3GHz) LINAC 20/12/2019 Nicolas.Delerue@lal.in2p3.fr

4. ThomX at LAL Nicolas.Delerue@lal.in2p3.fr

5. Source RF(v1) Source RF (v2) Baies Diag Ampli RF Baies Mag Baies Vide 0 5 10 • xxx Salle laser Mur de blindage FP X Salle climatisée Blocs de béton Flux class 100 Ligne X Extension possible Cooling RF anneau Salle Streak Blocs de béton Kicker Septum Nicolas.Delerue@lal.in2p3.fr

6. Main parameters • Electrons:- 20-70 MeV (nominal: 50 MeV)- 1nC- 20ps rms • Laser:- 30mJ/pulse => 100kW in Fabry-Pérot cavity- 1ps rms • X-rays:- 6-92keV- 1011 to 1013 ph/s Nicolas.Delerue@lal.in2p3.fr

7. Predicted flux Nicolas.Delerue@lal.in2p3.fr

8. RF Gun • Based on LAL experience: design similar to that built for CTF3 (CLIC) • 2.5 cells, 80MV/m, 6MW, 3 GHz • Q=14400 Nicolas.Delerue@lal.in2p3.fr

9. RF Gun (2) • CTF3 RF Gun was designed, built and brazed at LAL. • Also using LAL’s experience with its own RF-Gun (PHIL) Nicolas.Delerue@lal.in2p3.fr

10. Linac • Rep. rate = 50 Hz • 5MeV to 70 MeV (nominal 50MeV) • S-Band (2998,55 MHz – European standard) • One LIL accelerating structure (nominal: 12.6 MV/m; can reach 18.3MV/m). • Total length: 6.45m Gun section LIL accelerating section Nicolas.Delerue@lal.in2p3.fr

11. Transfer line (from A. Loulergue) Nicolas.Delerue@lal.in2p3.fr

12. Ring injection • Injection angle: 150mrad • Septum: 1kA – 150V (50ns) • Injection angle compensated by kicker • Currently studying a scheme with injection and extraction Nicolas.Delerue@lal.in2p3.fr

13. Ring Nicolas.Delerue@lal.in2p3.fr

14. Ring optics Nicolas.Delerue@lal.in2p3.fr

15. Beam dynamics • CBS makes the beam lifetime very short=> beam stored for only 20ms • Damping is very long (1-2s) • Injected bunch is very short (4ps)=> turbulent process to fill the bucket (20ps) • Strong collective effects (CSR, Resistive walls, …) (from A. Loulergue) Nicolas.Delerue@lal.in2p3.fr

16. Beam dynamics (2) Nicolas.Delerue@lal.in2p3.fr (from A. Loulergue)

17. Main diagnostics • Energy spread measurement prior injection • Bunch length measurement before injection (Cerenkov) and in the ring (SR) using a streak camera • Longitudinal and transverse feedback to minimise instabilities using BPM information • Laser follows the e- beam position • Extraction dump: Imaging station to allow beam dynamics studies Nicolas.Delerue@lal.in2p3.fr

18. Extraction • Beam will be extracted after 20ms. • Reduces radiation • Diagnostics on extracted beam • Details still under study Nicolas.Delerue@lal.in2p3.fr

19. Lasers system Chirped Pulse Amplifier • Based on our experience with MightyLaser • Fibre amplification • Lower rep. rate:37.7MHz (instead of 178MHz) => Larger oscillator cavity… • Higher power (Goal 100W) • => Much higher energy per pulse: 281nJ => 2.6 uJ • Need to address carefully non linear effects=> larger fibre, more stretching • Using advanced R&D done at CELIA Master (low power) Oscillator 200 mW Stretcher Power amplifiers 100 W Compressor Nicolas.Delerue@lal.in2p3.fr

20. Fabry-Pérot cavity • Also based on our experience with MightyLaser • 4-mirror cavity but with a planar geometry • Lower frequency requires longer path (8m) • Digital feedback will use the same principle but using a home-built system (better control) • A first in-air prototype has been tested this summer at LAL. Nicolas.Delerue@lal.in2p3.fr

21. Fabry-Pérot cavity (2) Optical path : ~ 8,4 meters (40 Mhz) e- Spherical Mirror 1 Spherical Mirror 1 Compton 20 mrad (half angle) Flat Mirror 2 Laser Flat Mirror 1 ~ 2100 mm Nicolas.Delerue@lal.in2p3.fr

22. Interaction area • Design of the interaction area is challenging • Elliptical beam pipe • 2 degrees crossing angle • Laser and X-rays slits • (R4,5x45mm et R 3x27mm) Nicolas.Delerue@lal.in2p3.fr

23. Vacuum issues • Ion trapping will be exacerbated by the high repetition rate. • This induces an increase of the relative pressure seen by the beam and some charge shielding. • => Important to have a very good vacuum • However these tight vacuum requirements conflicts with the Fabry-Pérot cavity feedback requirements => R&D in progress to see what can be achieved. Nicolas.Delerue@lal.in2p3.fr

24. X-ray line • Several instruments to caracterize the X-rays (focalisation, position, profile, intensity…) during comissioning. • Radiation safety still under study. Nicolas.Delerue@lal.in2p3.fr

25. Applications • Heritage applications (Collaboration with C2RMF / Musé du Louvres)- Structural and chemical studies of artefact- Compact source can be installed in a museum => Imaging of artefact in situ • Medical application (Collaboration with ESRF)- Imaging using k-line of elements- High energy radiotherapy (specific tumors)- Radiotherapy with radiation enhancement (CisPt)=> ThomX is more flexible then ESRF Nicolas.Delerue@lal.in2p3.fr

26. Application to positrons • ThomX energy is too low for positron production • However the experience gained operating ThomX will be applicable to a Compton based positron source. • In particular this will be an opportunity to study the dynamics of a beam undergoing strong Compton interactions. • ThomX is a step toward the demonstration of Compton based polarised positrons sources. Nicolas.Delerue@lal.in2p3.fr

27. Thank you Nicolas.Delerue@lal.in2p3.fr