Non—destructive transverse emittance measurement device

1. Non—destructive transverseemittance measurement device C. Gabor, J. Pozimski, A. Letchford The Front End Test Stand Collaboration

2. Outline Introduction FETS, Photo detachment & basic principle of beam diagnostic Theoretical investigations Proof of principle experiment Demonstration experiment at a small H- beam line in Frankfurt Further Hardware Summary & Outlook

3. Layout of the Front End Test Stand FETS at David Lee and Juergen Pozimski, Imperial College 3MeV beam energy, ~ 60mA H- 50Hz, <2ms (10% duty cycle)

4. Photo Detachment H— beam diagnostic • non destructive (i.e. no mechanical parts inside the ion beam) • => minimizing the influence on the H- beam (on line) • highly suitable for high power applications like FETS • different applications possible: profile(s), emittance • ~ electrons, neutrals, laser power attentuation • ~ more information about beam are possible, also with good resolution • ~ separating neutrals and H- can cause less flexibility because of dipole • ~ higher costs compared with a traditional emittance scanner

5. Non-destructive, transverse H- emittance measurement Comparission with a slit—slit emittance instrument: 1st slit is replaced by a laser 2nd slit is replaced by a scintillator with CCD camera  more information (than 2dim) about phase space Only a small portion of H- will be neutralized, i.e. max. portion of laser interaction

6. Different emittance measurement principles Envellope of the ion beam Cross section of the ion beam Slit—slit Principle : only 2dim phase space e = e 2dim (y,y') Point—point Principle : full 4dim information about phase space

7. Photo detachment simulations aboutits transfer function phase space neutralized particles, drifted particles beam profile Left, beam profile I(y') integrated of the emittance pattern and integration of drifted, (100mm) neutralized particles (dots). Right, the "neutralized particles" at +/-10mm and the drifted particles, enclosed by the neutralized patterns, are shown.

8. Comparision of simulation & measurement prf139.spe Y’ 2dim yy‘ emittance simulation close to the experiment y=+8,4mm experimental results at different laser positions prf101.spe y=-3,8mm simulation of photo neutralized ions of the xy distribution (drift length 500mm X

9. Further, current development work Limiting spatial resolution arc lenght: 500 mm deflection angle: 60 deg B—field: 0.522 T • homogeneity (waist) along the H- ion beam (collimation/ focusing) • different angles within scanning region space for piezo driven stages vacuum vessel

10. Summary -- Introduction about Photo detachment ion beam diagnostics Motivation; different principles of diagnostic using photo detachment; Comparison with other emittance measurement methods -- Theoretical aspects investigations about transfer function of "slit—point" emittance -- Proof of principle experiment in Frankfurt, Germany Outlook and recent work Further hardware: diagnostic dipole & laser equipment testing laser beam line/ movable mirrors particle detector (beam test of scintillators like P43, 45 improving theoretical understanding Longitudinal emittance measurement

12. Spare slides

13. Piezoelectric motors: status Motion controller Encoders Amplifiers and power supplies Rotary stage Linear stage

14. Motivation for non-destructive diagnostics xy intensity distribution of H-, 35keV 45mA, (Ion source test stand) Measurements at the current ISIS RFQ Water cooled end plate of a Fast Faraday Cup (unfocused ion beam) 665keV H- 1...3% dc 30....40mA 500 W/cm2 Scintillator image of H- ion beam after the ion source => beam not cylindrically symmetric mainly caused the slit extraction of the ion source (by Alan Letchford)

15. Some data about Front End Test Stand FETS

16. Integration of a photo neutralized& drifted H- distribution CCD image (raw data) + P43 with Alu y Dy x Relationship between y, Dy and y'

17. Laser characterisation, beam guiding Power meter CCD camera Attenuation Switching mirror Laser lab at Imperial college