Status Report on Mk.II Pepperpot Simon Jolly Imperial College 13 th June 2007

13/6/07Simon Jolly, Imperial College2 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.

13/6/07Simon Jolly, Imperial College3 Vacuum bellows Camera Moving rod Shutter Mounting flange Pepperpot head Bellows Tungsten mesh Beam profile head FETS Pepperpot Design

13/6/07Simon Jolly, Imperial College4 Pepperpot Installation

13/6/07Simon Jolly, Imperial College5 “0 mm” position of pepperpot head is 57 mm downstream of cold box exit. 458 mm dynamic range means “300 mm” position is approximately 20 mm upstream of slit- slit scanners. 57 mm Pepperpot Location Inside Ion Source 458 mm 100 mm Measurements taken at 100 mm intervals.

13/6/07Simon Jolly, Imperial College6 Mk.II Pepperpot Recent Improvements Completed: –Multiple calibration markings on pepperpot and profile heads. –Sliding camera mount to improve resolution. –Larger, permanent camera-bellows mount (not cardboard!). To do: –Background light replacement to improve calibration. –Support for new bellows mount. –Clamp to support sliding mount to prevent it toppling forward. –Install new components: Tuesday 16 th June?

13/6/07Simon Jolly, Imperial College7 Pepperpot Data Image Raw dataCalibration image Colour enhanced raw data image, 60 x 60 mm 2. Calibration image: use corners of 9 mm x 9 mm square on copper plate to give image scaling, tilt and spot spacing.

13/6/07Simon Jolly, Imperial College8 Pepperpot Emittance Extraction Pepperpot image spots: hole positions (blue) and beam spots (red) Emittance profiles Y X

13/6/07Simon Jolly, Imperial College9 13 kV Extract: 0 mm

13/6/07Simon Jolly, Imperial College10 13 kV Extract: 100 mm

13/6/07Simon Jolly, Imperial College11 13 kV Extract: 200 mm

13/6/07Simon Jolly, Imperial College12 13 kV Extract: 300 mm

13/6/07Simon Jolly, Imperial College13 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

13/6/07Simon Jolly, Imperial College14 Results of Position Variation Behaviour as expected: steady expansion in beam size along the beam axis. Emittances show no obvious nonlinearities; increases may be a result of space charge effects. Level of space charge compensation needs to be investigated with beam dynamics simulations. Flat top and bottom of the beam profile are likely due to collimation occurring upstream of the ion source exit.

13/6/07Simon Jolly, Imperial College15 6 kV Extract: 0 mm

13/6/07Simon Jolly, Imperial College16 9 kV Extract: 0 mm

13/6/07Simon Jolly, Imperial College17 13 kV Extract: 0 mm

13/6/07Simon Jolly, Imperial College18 17 kV Extract: 0 mm

13/6/07Simon Jolly, Imperial College19 Variation of Extract Voltage at 0 mm 6 kV 9 kV 13 kV 17 kV  x = 0.25  y = 0.77  mm mrad  x = 1.36  y = 1.47  mm mrad  x = 0.74  y = 1.14  mm mrad  x = 2.02  y = 1.92  mm mrad

13/6/07Simon Jolly, Imperial College20 Results of Extract Variation Distinct change in beam shape, density distribution and emittance: –6 kV shows strong asymmetric divergence in both planes. –9 kV shows mostly vertical expansion. –13 kV is nearly symmetric and slightly collimated. –17 kV dominated by collimation. A number of factors contribute to changes: –Upstream collimation. –Change in extract potential: changes shape of field within extract region, and affects shape of discharge plasma. –Increase in extract potential also requires change in 90° sector magnet current: change focussing effect of fringe fields. –Decrease in post-acceleration voltage means transverse focussing from fringe fields within post-acceleration gap will change.

13/6/07Simon Jolly, Imperial College21 Results Summary Extract (kV) Current (mA) Z (mm)Beam size  (  mm mrad) x (mm)y (mm)  x,rms  y,rms ± 1 ± 0.1± 3± 5 %

13/6/07Simon Jolly, Imperial College22 Scintillator Measurements 5 kV Ext5.5 kV Ext6 kV Ext6.5 kV Ext 7 kV Ext8 kV Ext9 kV Ext11 kV Ext

13/6/07Simon Jolly, Imperial College23 Scintillator/Pepperpot Comparison: 6 kV

13/6/07Simon Jolly, Imperial College24 Scintillator/Pepperpot Comparison: 9 kV

13/6/07Simon Jolly, Imperial College25 Conclusions First results already promising. Detailed research program under discussion: start with categorising scintillator. Clear comparison between scintillator and pepperpot measurements: calibration markings should allow precise correlation between the two. Quality of results should improve with latest modifications. Lots of data to take…