1. Resolution studies with scintillators. 1 Minjie Yan 1 G.Kube, 2 W.Lauth 1 Deutsches Elektronen-Synchrotron (DESY) 2 Institute of Nuclear Physics, Mainz Mini-Workshop PSI, 11.Mar.2013

2. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 2 Outline > Motivation Problem of COTR Scintillation screen as an alternative choice > Simulation with ZEMAX > Measurements at MAMI > Summary and Outlook

3. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 3 Motivation > Suppression of COTR by using scintillator screen > Remaining problem OTR generation at boundary scintillator/vacuum > 2 ways to circumvent the problem of coherent OTR: Temporal separation Spatial separation > Resolution of scintillator screens need to be studied

4. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 4 Simulation with ZEMAX Line source inside the crystal Scintillator characterized with refractive index n(λ) Central wavelength considered 10 8 rays are emitted homogeneously The ray tracing ends at a detector representing the camera

5. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 5 Simulation with ZEMAX Tracing results is the 2-D point spread function (PSF) of the line source Convolution of the PSF with a gaussian beam simulates the camera image

6. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 6 Simulation with ZEMAX > Investigate the influence of 3 factors on the beam profile resolution: Screen tilt Scintillator material Scintillation screen thickness > Scheimpflug principle considered in the simulation

7. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 7 There always exists an optimum screen tilt angle: tilt away from camera! Placing detector under 45˚ with respect to the beam axis seems to offer better resolution Scintillator material doesn’t influence much the optimum screen tilt Simulation with ZEMAX Influence of observation geometry

8. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 8 Simulation with ZEMAXBGO, Det45deg Thicker scintillation screen shows worse resolution The optimum screen tilt angle is not affected by the thickness of the scintillation screen BGO, camera at 45deg

9. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 9 MAMI measurements 855MeV cw electron beam: 3.2nA Goniometric stage equipped with different screens OTR screen as reference No Scheimpflug CCD camera (JAI BM- 141GE)

10. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 10

11. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 11 MAMI measurements CRY19(CRYTUR) offers the best resolution. Resolution of different materials

12. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 12 Influence of observation geometry OTR screen BGO screen, Θ =15⁰ BGO screen, Θ =45⁰ BGO screen, Θ =55⁰ Observation geometry has considerable influence on resolution. BGO screen, Θ = -25⁰ BGO screen, Θ =0 ⁰ BGO screen, Θ =25⁰ OTR screen MAMI measurements

13. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 13 Influence of observation geometry MAMI measurements Possible reason for the deviation between the simulation and measurements: - Scheimpflug - elliptical shape of the beam - incomplete simulation model?

14. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 14 Thicker scintillation screen shows worse resolution. MAMI measurements Influence of screen thickness

15. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 15 Summary and Outlook > Observation geometry has a considerable influence on the spatial resolution. > Implementation at FLASH Camera at 90deg, CRY19 screen (100um) at 35deg. CRY19 can easily get broken. Spatial separation of COTR will be tested. > Continue search for optimum scintillator material The same scintillator with different doping-material The same scintillator with different doping-concentration Powder scintillator > Implementation at E-XFEL

16. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 16

17. M. Yan, Mini-Workshop, PSI, 11.3.2013 | Page 17 Thank You