1. David Johnson –APC -

2.  The Proton Improvement Plan is tasked with Booster upgrades which will increase the Booster throughput required for future operation while maintaining acceptable losses.  Ultimate goal: 2.2E17 protons/hr @ 15 hz by 2016  Breaks down as: 3.7E15/min -> 6.1E13/sec -> 4.1E12/pulse -> assuming 10 turns (22 us linac pulse length) -> 4400 linac bunches per cycle -> 9.3E8 per bunch.  For numbers sake let’s just use 1E9/200MHz  Notching in the Booster ring deposits the removed bunches in the gradient magnets. This represents on the order of 30% of Booster losses ( few % of beam intensity).  Ultimately one needs about 30 -40 ns notch in the beam at extraction time for the extraction kicker rise time.  In the 200 MHz beam structure this would correspond to ~8 200 MHz bunches every 2.2 us and for 10 turns this would be a total of about 60 to 80 bunches or about 1-2% of injected beam.  Assuming 1E9/bunch this would be 6 to 8E10 /pulse but for simplicity lets assume 1E11 H- need to be neutralized per pulse. At 15 Hz -> 1.5E12/sec -> 100 watts of beam power to be removed.

3.  QUESTIONS:  Can we move the notching function out of the ring and provide a shielded dump for the H0 beam removed?  Early notching experiments by Ray (circa 2000 and before)) were done at 750 keV at the 90 deg bend. They demonstrated a 25-30 ns notch as seen at Tank 2 BPM. With the addition of the RFQ the interaction region would have to be just after the RFQ or at the entrance to tank 1, where there are vacuum windows.  There is another location, just upstream MV2 and MW06, that contains a dipole (MV2) to remove the H0 into a beam bump.  Can we utilize an optical notching system similar to that proposed for Project X?  See Project X docs 909 and 911 on Laser Chopper for Project X.  What are the requirements for this notching system?  Laser pulse energy (peak power)  Laser system (how can the required laser pulses be generated?)  Optical system / delivery system  Controls

4.  Assume the laser beam has a uniform irradiance and fully encompass’ the H - beam.  When the probability of interaction is high, and the interaction mechanism is not dependent on intensity (i.e cross section is not dependent on laser flux), the single interaction detachment rate, F 1, can be expressed as  where fluence is the number of photons per cm 2 at the interaction point,  laser is the laser pulse length,  is the photoneutralization cross section [cm2] and  crossing is the transit time of the H- across the laser beam [sec].  The photon flux is transformed like the photon frequency (energy) which, which like the energy is ~ the same in the lab and CM. where

5.  Assume a laser pulse length,  laser, of 500 ps, the single pass neutralization fraction as a function of laser pulse energy for several laser beam radii may be calculated.  For ~100% neutralization need to have ~10 to 30 mJ per laser pulse  At 325 MHz rep rate this corresponds to a 3 to 10 MW laser ! At this point everyone says it can’t be done. But can these numbers be beat down ? Laser Beam Radius Q-switch 10’s to 100’s mJ 10-100’s Hz

6. launch box optics box laser transport vacuum chamber chute Q8 Mirror boxes H0 waste dump H- to Booster Current laser profile monitor insert is 1.14 m *MAX 10 bunches/notch *10 notch/inj*1E9/bunch = 1E11/pulse*15 Hz = 1.5E12 particles/sec- ~ 100 W*

7. MW06 Laser beam size needs to enclose the smaller of the Booster beam dimensions i.e 6*1.3 ~ 7.8mm Can the linac vertical beam size at MW06 be reduced? Is this optical model of the lattice accurate? Data: March 2011

8.  To maximize neutralization and minimize the required laser power we want to make sure that the C.M photon energy is near the peak of the cross section.  The lab laser wavelength is dependent on the geometry between the laser and the H- beam.  Photoneutralization cross section of H- by incident photons of energy E is given by:  where  max is 4.2E-17 cm 2 and E 0 is 0.7543 eV. At 400 MeV,  = 0.7128 and  = 1.4258, with ion velocity of 2.138E8 m/s.

9. Assume the following geometry of the H- and laser beam. [From: Shafer LA-UR 98-2643] The photon energy seen by the H- electron in it’s rest frame is  = 180 : head on interaction

10.  For multiple interactions  Assume 99.95%reflectivity  Total neutralization~ N*single interaction  Laser beam size constrained by smallest H- beam size (i.e. Vertical)  Requires 1 um laser Single Interaction Multiple Interactions  For single interaction  Interaction length(time) ~x_ laser size/sin(180 -  )  Interaction length must be smaller than bunch separation  Requires 2 um lab frame laser

11. 11 24.2 us (~ 11 Booster turns) 2.2 us 67 ms ~22-25 us 5 ns (bunch spacing) ~500 ps bunch length 200 MHz bunch spacing 450 kHz “notch” spacing 15 Hz macro pulse rep rate MACRO MINI (11 turns) MICRO 2.2 us 10-12*5ns = 50 -60 ns If each notch created by a single 30-40 ns laser pulse with a pulse energy of 65 mJ. Implies 10 lasers timed to generate 10 notches each Booster cycle (15 Hz reprate) or a cavity with 2.2 us delay

12. 12 2.2us 50-60ns ~22 us ~500 ps 5 ns ~1 ns ~500-600 ps ~100-200 ps Laser temporal profile for a single bunch Burst of 6 to 8 laser pulses at 200 MHz This provides about 4 ns between laser pulses (or reduces requirements on rise/fall time of laser pulse)

13. CW 100 mW Narrow line width Seed laser Pulse pattern generator Fiber Amp Pre-Amp Gain ~ ? 10GHz modulator Amplifier Gain ~ ? Coupling Optics Zig-zag cavity w/ 40 reflections Input pulse to cavity: ~1 -3 mJ, 0.5ns, burst mode 100 pJ (0.5 ns) 200 MHz 10-100 nJ (0.5ns) 200 MHz Couple to free space optics 1-3 mJ (0.5 ns) 200MHz/450 kHz burst TIMING Card /lock Approx 1 m length 450 kHz bursts 2 to 20W 46 to 460 mW Top Hat Converter r=5mm 1/e P peak =3mJ/.78 cm 2 in 500 ps = 3.8 mJ/cm 2 in 500 ps MAX

14.  Energy 400.000000 [MeV]  Linac current 30 [mA]  Linac bunch intensity 9.355704e+008 [ppb]  Beta 0.712832  Gamma 1.425852  H- velocity 2.138495e+008 [m/s]  RFQ frequency 200.000000 [Mhz]  Bunch spacing 5.000000 [ns]  Bunch length +/-19.500000 [degrees]  Bunch length (full) 11.583514 [cm]  Bunch length (full) 0.541667 [ns]  RMS beam size: H 0.13 [cm] V 0.13 [cm]  100pct beam size: H 0.78 [cm] V 0.78 [cm]

15.  Laser Energy 1.000000e-003 [Joules]  Pulse length 5.958333e+002 [ps]  Laser beam area 7.361640e-001 [cm^2]  Spot size: H 0.86 [cm] V 0.86 [cm]  Photon wavelength 1030 nm  Lab Frame Photon Energy 1.931068e-019 [Joulse] 1.204433e+000 [eV]  Photons per pulse 5.178482e+015  Photon rate 8.691158e+024 [photons/sec]  Photon fluence 7.034413e+015 [photons/cm^2]  Photon flux 1.180601e+025 [photons/cm^2/sec]  Laser Peak pulse power 1.678322e+000 [MW]

16.  Distance between crossings 2.000000e+000 [cm]  Distance between reflections on mirror 4.000000e+000 [cm]  distance laser travel between crossing 1.402856e+000  cavity radius 5.000000e+000 [cm]  Incident angle 1.130993e+001 [degrees]  Crossing angle 78.69 [degrees]  Lorentz Factor 1.226521e+000  Rest frame photon energy 1.477263e+000 [eV]  Rest frame wavelength 8.397737e+002  crossing time per interaction 2.045812e-010  Number of passes 40.000000 total crossing time ~ 8 ns  Cross section in rest frame 4.197165e-017 [cm2]  Photon flux in H- rest frame 1.448031e+025 [photons/cm^2/sec]  Mirror Reflectivity 9.995000e-001  Average Neutralization factor per interaction 1.147403e-001  Total Neutralization 9.923647e-001  Multipass insertion length 7.800000e+001 [cm]  Total laser path length 1.094227e+000 [m]  Peak laser pulse power 1mJ/600ps : 1.6 MW  Average 200MHz power of laser 8*1mJ pulses per 40 ns 200.000000 [kW]  Average power of laser for each injection (10 notches in 22 us) 3.6 kW  Over all average power of laser system at 15Hz ~ 1.2 W

17. 50 mJ “10 ns pulse”

22.  Beamline  Will both H0 and H- fit through the downstream end of MV2 or do we need larger aperture? initial look seems OK  Will H0 beam miss the first quad downstream of MV2 or is a lattice modification necessary? To be determined  Need to support downstream quads with new stands. Just engineering, no show stopper  Size of H0 dump (similar to MTA absorber) maybe 12” diameter and 30 “ long. Should fit under downstream quads.  Notcher  Laser system (seed + amplifier)  Zig-zag optics (in vacuum)  Controls