Filamentation effect in a gas attenuator for high-repetition-rate X-ray FELs.
J Synchrotron Radiat
; 23(1): 21-8, 2016 Jan.
Article
in En
| MEDLINE
| ID: mdl-26698041
ABSTRACT
A sustained filamentation or density depression phenomenon in an argon gas attenuator servicing a high-repetition femtosecond X-ray free-electron laser has been studied using a finite-difference method applied to the thermal diffusion equation for an ideal gas. A steady-state solution was obtained by assuming continuous-wave input of an equivalent time-averaged beam power and that the pressure of the entire gas volume has reached equilibrium. Both radial and axial temperature/density gradients were found and describable as filamentation or density depression previously reported for a femtosecond optical laser of similar attributes. The effect exhibits complex dependence on the input power, the desired attenuation, and the geometries of the beam and the attenuator. Time-dependent simulations were carried out to further elucidate the evolution of the temperature/density gradients in between pulses, from which the actual attenuation received by any given pulse can be properly calculated.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
J Synchrotron Radiat
Journal subject:
RADIOLOGIA
Year:
2016
Document type:
Article
Affiliation country:
Estados Unidos