1. Conveners: L.Serafini,F. Villa
WG2 - Photon Machine (Lasers and Optics) including:   - Physics of and with Comtpon Sources, Detectors - γ-γ and e--γ colliders
Conveners:
L.Serafini,F. Villa

2. LINAC design: user requests
Neutron source
with TOF
Nuclear photonics
g - g collider
(SASE, seeded)
FEL
FEL (oscillator)
THz radiation
e+- e- collider
e-- e- collider
E beam energy [GeV]
qb bunch charge [pC]
st bunch length [fs]
sx,y bunch transv. size [mm]
sE /E bunch energy spread [10-3]
en bunch norm. emittance [mm]
fb bunch rep. rate [MHz]
Tp pulse duration [μs]
fpulse pulse rep. rate [Hz]
Ip current in the pulse [mA]
Iave average current [μA]
(DE/E)train energy spread along the train [10-3]
Pb beam peak power [kW]
<Pb> ave. beam power [kW]
L luminosity [cm-2s-1]

3. Beam temporal structure: pulsed vs. CW
(...)
Down to 200 ns (up to 5 MHz)
Approx 1 ms
(...few 1000s...)
100 ms (10 Hz)
Pulses
Continuous
wave

4. More in detail: Questions (see WG1): γ-beam & e- beam polarization
Fabry-Perot recirculator discussion
Interaction region/s
Questions (see WG1):
Is there a machine configuration capable to serve all (or most of) the users?
Which users may share the same injector (i.e. how many injectors do we need)?
Which users may share the same beam?

5. WG2 summary: Photon factory
Fabry-Perot:
Request performance somewhere in between LAL experience and SAPPHIRE proposal: 100KW state of the art, 1MW required.
Mechanical stability and mirror cooling problems.
No place for γ-γ inverse coming interaction
No place for e- beam magnetic removal
Eli-like recirculator:
Higher misalignment sensitivity -> demanding fabrication procedure
γ-beam polarization precession plus dicroism to check, from code simulation Lint=98% over 32 passes
Circular polarization preservation?
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6. WG2-3 summary: e-beam temporal structure
Looking at the Luminosity preservation in the two possible RF beam scenarios:
The γ-γ, and e– γ colliders prefer the pulsed RF regime: high charge/bunch value.
The e- e-, e-e+,e- on target , the same but the RF pulse is under study, if longer, more crowded…
Nuclear photonics CW agreement, but same as above, advantage from Fel based Compton source.
Polarization features have to be studied in detail to provide final percentage and preservations for both beams . Add a WG on white book?
Final goal summary table in the very next days.
Advanced Positron source under study as well.
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