FETS H - Ion Source Experiments and Installation Scott Lawrie, Dan Faircloth, Alan Letchford, Christoph Gabor, Phil Wise, Mark Whitehead, Trevor Wood, Mike Perkins, Mick Bates, Pete Savage, David Lee, Juergen Pozimski, Rafael Enparantza

Front End Test Stand (FETS)

Beam Parameter ISIS Ion Source FETS Ion Source Total Energy35 keV65 keV Current 55 mA (35 mA to LEBT) 60 – 70 mA Rep. Rate50 Hz Pulse Length200 μ s2 ms Normalised x emittance 0.9 π mm mRad0.5 π mm mRad Normalised y emittance 0.8 π mm mRad0.5 π mm mRad

Main Modifications Post extraction acceleration gap Analysing dipole magnet Extraction electrodes Power supplies

250µs Pulsed Extraction Power Supply + 17kV - 90° Analysing Magnet 35 keV H - Beam 55 mm Post Extraction Acceleration Gap Platform Ground Platform DC Power Supply Laboratory Ground -35 kV kV Extraction system ISIS Ion Source

2ms Pulsed Extraction Power Supply + 25kV - 90° Analysing Magnet 65 keV H - Beam 9mm Post Extraction Acceleration Gap Platform Ground Platform DC Power Supply Laboratory Ground -65 kV kV Extraction system FETS Ion Source Proton Suppressor

Post Extraction Acceleration Gap

ISIS LEBT Line Ion source Post Extraction Acceleration Solenoid 1Solenoid 2 DiagnosticsSol. 3

FETS LEBT Line Ion source Post Extraction Acceleration PLUS Diagnostics Solenoid 1Solenoid 2 DiagnosticsSol. 3

Steel mounting and pumping flange Laser diagnostics dipole apparatus Electrode and mu-metal shielding assembly Ion source, analysing dipole magnet and cold box

Electrode Spacer Assembly

Analysing Sector Magnet

Reasons For Use of Dipole Analyse out co-extracted electrons Allow caesium to collect in cold box Modify beam from slit to round shape Weakly focus beam to LEBT entrance Convenient 90° loading geometry

Field Stronger Field Weaker Field Stronger Field Weaker Axial Beam Size Angle Around Dipole 90° 0° Angle Around Dipole Radial Beam Size 90° 0° Magnetic Field Index: n > 1 n = 1 n < 1

Predicted beam profiles Measured beam profiles n > 1 n = 1 n < 1

Extraction Electrode Setup

Beam Parameters Determined by Extraction System: Ion species (H - ) Current needed for application (70 mA)  High current density at plasma aperture  High extraction voltage: Low divergence angle ( ε < 0.5 π mm mRad)  Concave plasma meniscus  Focussing electrostatic lens geometry  Space charge compensation  Low ion temperature

Standard ISIS Extraction Geometry

Pierce- Style Extraction Geometry

Alternative Pierce- Style Geometry

Overview of Experimental Work

Norm. ε h = 0.82 π mm mRadNorm. ε v = 0.75 π mm mRad ISIS Ion Source 46.6 mA

Norm. ε h > 0.69 π mm mRadNorm. ε v > 0.45 π mm mRad ISIS Ion Source Reduced Post-Extraction Acceleration Gap mA

Norm. ε h = 0.68 π mm mRadNorm. ε v = 0.42 π mm mRad ISIS Ion Source Reduced Post-Extraction Acceleration Gap + Improved Sector Magnet Good Field Region mA

Norm. ε h = 0.57 π mm mRadNorm. ε h = 0.39 π mm mRad ISIS Ion Source Improved Sector Magnet Good Field Region + Reduced Post-Extraction Acceleration Gap + Pierce-Style Extraction Geometry mA

FETS Ion Source Installation Progress

Questions? Ion Source Latest Status: Commissioning timing signals Mains operable on platform Platform 70 kV imminent Extract power ready Beam due very soon!