Idea: thin SiN membrane (100 nm) · LBDP Rb vapor Pros: • one single thin membrane on the...
Transcript of Idea: thin SiN membrane (100 nm) · LBDP Rb vapor Pros: • one single thin membrane on the...
Idea: thin SiN membrane (100 nm)
e- beam
p+ beamlaser beam
SiN membrane
LBDP
Rb vapor
Pros: • one single thin membrane on the electron beam path (small scattering angle) • LBDP stops both laser pulses
laser beamx
~1m
B
SM’or ACC’or
Check beam optics• Multiple scattering calculations may not be valid
because thickness << X0
• Check scattering angles with FLUKA simulations
• Agreement between simulations and MCS theory
Beam size at the foil• Calculate σ at the foil
• According to beamline design, the distance foil-waist can’t be < 1m (dipole dimensions constraints)
• Maximum window size: 10x10 mm^2
thickness cannot be > 100 nm
Betatron function• Calculate β* given initial normalized
emittance (20 mm*mrad) and longitudinal position of the waist w.r.t. the foil
• According to beamline design, the distance foil-waist can’t be < 1m (dipole dimensions constraints)
• First cons: β_in < β*
𝛽∗ =𝜀𝑜𝑢𝑡𝜀𝑖𝑛
∙𝑧 𝑜𝑢𝑡𝑧𝑖𝑛
∙ 𝛽𝑖𝑛
>1 <1
Emittance• Calculate εN given initial normalized
emittance (2 mm*mrad) and longitudinal position of the waist w.r.t. the foil
• According to beamline design, the distance foil-waist can’t be < 1m (dipole dimensions constraints)
• Second cons: emittance growth is higher than in the two-foil setup
𝜀𝑜𝑢𝑡2 = 𝜀𝑖𝑛
2 + 𝜎𝑓2𝜗2
Beam envelope• According to beamline design, the distance
foil-waist can’t be < 1m (dipole dimensions constraints)
• According to beamline design, quadrupole magnet is positioned ~2 m away from the dipole magnet
• Third cons: beam size at the magnet > quadrupole aperture
Conclusion• Even if it simplifies the setup, it is not feasible for the beam optics
Conclusion• Even if it simplifies the setup, it is not feasible for the beam optics• Two-foil setup is technically more complicated but feasible
Other solutions:
• One single foil acting as vacuum window and LBDP
• Only one LBDP, SiN membrane upstream at a waist• meaning: last part of the beamline has to be hot
LBDP1
VACUUM WINDOW 1
VACUUM WINDOW 2 + LBDP2
e- beam
p+ beam
LBDP
e- beam
p+ beam
hν hν
SM’or ACC’or
SM’or ACC’or