Pre-Mono Transmission Sample Chamber (Open Access)
There will be an experimental station before the monochromator, experimental position 1, where samples can be introduced into the unfocused, ~1 mm in diameter, beam. Several detection methods are potentially possible. The proposal is to concentrate on transmission through thin samples, using the monochromator in spectrograph mode, with a detector at the exit slit to measure absorption spectra.
The absorption experimental set up is simple. An x-y manipulator is required to position the samples in the beam. The sample positioning system does not need to be high precession due to the large beam size. There will be a camera to monitor sample position and to align the FEL, the pump laser and an alignment laser into overlapping phase space at the sample position. The sample positioner will carry a number of samples which will include a Ce doped YAG crystal for alignment of the FEL pulse.
The sample chamber will be isolated from the SOMS and the monochromator optics by an all metal gate valve. The chamber will have an ion pump for UHV operation and a cold cathode gauge to monitor the pressure. The pressure in this system will have to be <5 x 10-9 torr to be opened to either the monochromator or the SOMS system. Samples will have to be UHV compatible.
The shielding requirements for this sample system have not been determined, but it should be anticipated that samples cannot be run in this system unless personnel are excluded from the first hutch. Access to the first hutch with samples in the beam can only be permitted when proper shielding has been defined, implemented and qualified.