Commissioning and Data Collection David Johnson Accelerator Physics Center Proton Source Department Meeting June, 23, 2011

 Concept  Linac Installation  Profile Examples  Hardware Issues  Optimization  Conclusions 2

 David Johnson (APC/HINS) group leader  Jim Zagel (AD/I) electronics and integration support  Carl Lundberg (AD/I) electronics and mechanical support  Dave Slimmer (AD/I) software support responsible for LabView  Jim Galloway (AD/I) electronics and mechanical support  Ray Tomlin (AD/PS) laser support guru  Vic Scarpine (AD/I) responsible for HINS LPM design and installation  Manfred Wendt (AD/I) provided button BPM's, and Inst. Dept. support  Kevin Duel (AD/MS) mechanical engineer for chamber construction and installation  Hogan Nguyen (PPD/SiDet) provided scintillator and PMT for electron detector  Vladimir Kashkin (TD) designed electron separation magnet  Peter Prieto (AD/I) Timing board design  Glenn Johnson (AD/I) timing board layout  Wayne Schmitt (AD/Safety) help with radiation measurements  Mark Lebrun (AD/MS co-op) radiation shielding design  Booster Department (particularly Todd and Kent) 3

 Utilize photons from Nd:YAG laser ( = 1064 nm) to photodetatch the outer electron from the H- ions creating neutral H0 atoms and free electrons.  Photodetachment cross section (for Nd:YAG) is ~3.8E-17 cm2  Fraction neutralized where F is photon flux and  is the crossing time  For a 50 mJ 10 ns laser pulse with an average laser size of 200 um, we neutralize about 92 % of the H- passing through the laser.  The liberated electrons are swept into electron detector by weak magnetic field.  With a laser beam diameter << H- beam, we can scan the laser across the H- beam and collect the electrons at each position of the scan thus giving us a density profile of the H- beam.  For typical source currents of ~ 35mA -> 200 MHz bunch intensities of ~1E9 with a bunch separation of ~5 ns. For a laser pulse duration of ~10 ns we impact only a single bunch each linac cycle. 4

launch box optics box laser transport vacuum chamber chute Q8 Mirror boxes 5

viewports (laser beam dump not shown) electron detector port button BPM optics box H- beam electron magnet 6

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 Scan limits determined by size of laser dump viewport  +/- 33mm/264mm-> 125mr  +/ o optical (+/3.58 o mechanical)  Beam center -> +/-20 mm scan limits  Mask at input viewport limits laser excursion to prevent launching laser up or downstream in vacuum chamber  Cambridge Technology scanner  +/- 1 degree/volt -> input voltage of 3.58V  Repeatability 8 microradians Optics Box 3” beam pipe Electron magnet pole tips 1 3/4 ” beam pipe Not to scale Viewport: AR coated 2.69”dia Anodized MASK Max angle +/- 6 o Anodized laser dump w/PD Mirror box 8

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YM1 LM1 LM2 LM1 LM2 CM1 A1 A2 10

Peak dipole field ~ 175 Gauss Integrated dipole field ~ +/- 70 G-m from each half of the magnet, Net integrated dipole ~ 0.61 G-m. Results in a displacement of ~0.4 mm and angle of ~19 ur. 11

 Electron energy 218 keV  Optical detection  Scintillator (polystyerene doped with N-Methyl-chloride) 3” diameter 1” thick with 100A aluminized coating on vacuum side and walls  Electron detection nearly 100%  25 ns dopant decay time  Scintillator made at FNAL  Photomultiplier Tube (Hamamatsu stage)  Currently using an 8 bit 1 Gs/sADC scope card in LPM computer to monitor PMT voltage into 50 ohms. 12

 See motion on downstream BPM’s. Peak distortion is seen at VPQ15 of something less than 2 mm and ~0.7 mm at VPFOIL. (This is well within the long term drift/tuning of injection positions)  NO impact on losses of injection efficiency is seen.  Orbit distortion at injection can be compensated (if desired by -0.5 amp on VTQ8) 13

PMT high voltage on/magnet offTurn on magnet (with PMT on) Move laser timing inside the beam pulse 14

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Multiwire Data taken March 23, 2011 $1D 11 4E12 LPM profile taken on June 8, 2011 On $14 cycle (single bunch) 18

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Scan range -18 to 18 mm PMT HV 700 V Small peak area ~ 2.3% of Main bunch Bunch intensity ~1E9 72 data points across scan 10 beam samples/data point Is this real beam or reflection? 20

Increase PMT voltage to 1 kV 21

 Laser power supply damaged by radiation  Moved power supply up stairs  Scanning galvanometers issues  Optical position feedback loop maxed out voltage  Suspect darkened led – working with vendor  Order new galvanometers  Axis select galvanometer issues  Not meant to operate in vertical orientation  Looking for suitable alternative 22

 Currently we are using laser at full energy to get a 10 ns laser pulse. This limits the PMT high voltage due to the limited dynamic range of the ADC.  We need to further optimize the laser energy/timing, PMT high voltage, and better understand the PMT signal and ADC.  Data analysis is just starting… 23

 The BLPM can parasitically and nondestructively measure transverse profiles of beam in the 400 MeV line.  Single (up to a few) bunch measurements possible at any selectable position within the bunch train.  The system is very sensitive and can be used to measure and characterize halo.  Data analysis and optimization just starting.  Lessons learned to be applied to future systems for HINS and Project X 24