1. G4Beamline Simulated Electron Distribution within the HPRF Cavity 2/15/20121

2. Protons Electrons Beam Collimators Cavity 1000 protons shown (the viewer didn’t like more than that) Stochastics on Tracking protons and electrons Beam originates at vacuum window 4 Detectors (not shown) – 3 in cavity, 1 near origin of beam 6 Detectors (not shown) – 5 in cavity, 1 near origin of beam 2/15/20122

3. Near Vacuum Window 100,000 protons p=954.263MeV/c σ x =2.5mm, σ y =4.0mm, σ p =100keV Proton X-Y distribution – Top left & right (zoomed in) (mm) Proton momentum distribution – right (MeV/c vs mm) 2/15/20123

4. Center of the cavity 950psi H2, 30MV/m (peak) X-Y Distribution (mm) Total momentum (MeV/c) vs r (mm) r up to 20mm Radial distribution (mm) 2/15/20124

5. 5mm Upstream of the center of the cavity Total momentum (MeV/c) vs r (mm) r up to 20mm Radial distribution (mm) More electrons produced upstream Slightly higher momentum Roughly same radial RMS at 2cm 2/15/20125

6. 5mm Downstream of the center of the cavity Total momentum (MeV/c) vs r (mm) r up to 20mm Radial distribution (mm) 2/15/20126 Fewer electrons produced downstream Slightly lower momentum Roughly same radial RMS at 2cm

7. Fitted Distributions – Electrons contained within r 2/15/20127 Top left – Fitted radial electron distribution at the center of the cavity (#e- vs mm) Top right – Fitted normalized radial electron distribution at the center of the cavity (mm) Right – Fitted normalized radial electron distribution for z= -8, -4, 0, 4, 8mm (0=center, - upstream, + downstream) Vertical line drawn at r=20mm (radius of downstream collimator) Horizontal lines at 90 and 95% total e- Fitted with an exponential of the form y(x)=a+b*exp(c*x)

8. Left – 5 detector planes hits Bottom - #e- contained within (r,z) Strong z dependence can be seen 587/746 e- 8mm upstream of center at r=20mm 231/290 e- 8mm downstream of center at r=20mm 2/15/20128 3D Distribution x y z r r z z Ne Beam

9. 2/15/20129 Conclusions ~80% of electrons fall within the radius of the downstream collimator Electrons more spread out the further downstream you go 90% of all electrons contained within 35mm radius 95% of all electrons contained within 50mm radius