Presentation on theme: "Pepperpot Emittance Measurements of the FETS Ion Source Simon Jolly Imperial College 3 rd October 2007."— Presentation transcript:
Pepperpot Emittance Measurements of the FETS Ion Source Simon Jolly Imperial College 3 rd October 2007
3/10/07Simon Jolly, Imperial College2 The Pepperpot Emittance Scanner Current slit-slit scanners give high resolution emittance measurements, but at fixed z-position, with x and y emittance uncorrelated. Correlated, 4-D profile (x, y, x’, y’) required for accurate simulations. Pepperpot reduces resolution to make correlated 4-D measurement. Moving stage allows measurement at different z- locations: space charge information. Possible to make time-resloved measurements within a single pulse. Added bonus: make high resolution x-y profile measurements.
3/10/07Simon Jolly, Imperial College3 Pepperpot Principle H - Ion Beam Tungsten screen Copper block Quartz screen H - Beamlets Fast CCD Camera Beam segmented by tungsten screen. Beamlets drift ~10mm before producing image on quartz screen. Copper block prevents beamlets from overlapping and provides cooling. CCD camera records image of light spots. Calculate emittance from spot distribution.
3/10/07Simon Jolly, Imperial College4 Pepperpot Components Pepperpot head: –Tungsten intercepting screen, 50 m holes on 3mm pitch in 41x41 array. –Tungsten sandwiched between 2mm/10mm copper support plates. –Quartz scintillator images beamlets. Camera system: –PCO 2000 camera with 2048 x 2048 pixel, 15.3 x 15.6 mm CCD. –Firewire connection to PC. –105 mm Micro-Nikkor macro lens. –Bellows maintains light tight path from vacuum window to camera. Main support: –Head and camera mounted at either end of 1100 mm linear shift mechanism, with 700 mm stroke. –All mounted to single 400 mm diameter vacuum flange.
3/10/07Simon Jolly, Imperial College5 Vacuum bellows Camera Moving rod Shutter Mounting flange Pepperpot head Bellows Tungsten mesh Beam profile head FETS Pepperpot Design
3/10/07Simon Jolly, Imperial College7 Diagnostics Vessel Beam Current Toriod X and Y Slit-Slit Emittance Scanners Movable Scintillator with Interchangeable Pepperpot or Profile Head Buffer Gas Delivery System Diagnostic Dipole Beam Shutter ISDR Diagnostics
3/10/07Simon Jolly, Imperial College8 Pepperpot Data Image Raw dataCalibration image Colour enhanced raw data image, 60 x 60 mm 2. Calibration image: use corners of 126 x 126 mm square on copper plate to give image scaling, tilt and spot spacing.
3/10/07Simon Jolly, Imperial College9 Pepperpot Emittance Extraction Pepperpot image spots: hole positions (blue) and beam spots (red) Emittance profiles Y X
3/10/07Simon Jolly, Imperial College10 Pepperpot GUI and Data Analysis
3/10/07Simon Jolly, Imperial College11 Position Variation for 13 kV Extract 0 mm 100 mm 200 mm 300 mm x = 1.36 y = 1.47 mm mrad x = 1.82 y = 1.96 mm mrad x = 1.65 y = 1.78 mm mrad x = 1.90 y = 2.04 mm mrad
3/10/07Simon Jolly, Imperial College13 Pepperpot vs. Slit-Slit: 11kV X Emittance 0.39 mm mrad
3/10/07Simon Jolly, Imperial College14 Pepperpot vs. Slit-Slit: 11kV Y Emittance 0.45 mm mrad
3/10/07Simon Jolly, Imperial College15 Emittance Cut Optimisation As with Slit-Slit scanner, pepperpot emittance measurement is sensitive to cut level. Have to impose some sort of cut due to inherent 100 count noise from camera and background noise. Need to optimise cut level to give consistent emittance measurement.
3/10/07Simon Jolly, Imperial College19 Conclusions 2-D profiles with high resolution (70 m) Medium resolved 4-D emittance measurements (3 mm, 7 mrad). Both data can be combined to produce 4-D data with high resolution. Clear correlation between pepperpot, profile and slit-slit emittance measurements. Emittance measurements at different z-positions allow investigation of space charge forces. Able to output data into GPT and LINTRA simulations.