Machine and Optics Hutch

The optics hutch OH1 is common for the ID10 EH1 and EH2 lines.

From the undulator source the beam encounters the following optical elements on its way towards the final beamstop in the EH2 hutch :

Undulators - Front end - Primary slits - White beam double mirror - OH1 1st monochromator - SS slits - Transfocator - OH1 beam shutter - EH1 beam shutter - CRLs - TS slits - OH3 monochromator - OH3 beam shutter (SCHEMATIC DRAWING)

Here follows a short description of the above mentioned elements:

Undulators

U27, U35 and U27/U35 revolver unit. Technical details can be found in Beamline Description (UNDULATOR SOURCE). The undulators are controlled by the ID application "idappli" running on the UNIX workstation ting.esrf.fr. Usually this application is visible on the terminal screen. In the ID application the undulator gaps are set and by choosing “automatic mode” the undulators will return to these values after an eventual opening due to beamloss etc. Note that the automatic mode expires after 6 days then the front end will close i.e. the beam is blocked. DO NOT CHANGE THE UNDULATOR GAPS ONCE THEY'VE BEEN SET! SPEC macros to calculate the undulator gap for a given energy are described in the ALIGNMENT GUIDE.

Front end

Contains photon absorbers (heat load filters) and the main beam shutter. The front end also marks the transition from the machine to the beamline.

Primary slits

In general the primary slits are not touched during normal operation. However, after each shutdown they are realigned (short description in the ALIGNMENT GUIDE).

Double mirror

The white beam double mirror is used to reject high undulators harmonics and reduce heat load on the monochromator. See the ALIGNMENT GUIDE for details.

OH1 monochromator

The monochromator is a cryo-cooled Si channel-cut working in vertical scattering geometry. It is used for the operation in EH1. When EH2 hutch operates the OH1 monochromator must be remove from the beam.

SS slits

The SS slits are used together with the TS slits (see later) as a collimator to define the beam size. A small beam size reduces the heat load on the monochromator (important!). Users should never touch SS unless a clear agreement has been made with the local contact. The SS slits are operated under SPEC which is the control language of the beamline ( ON-LINE SPEC MANUAL). SS consists of two l shaped slit blades that can be operated independently. The SPEC command

mv ssvg 0.1

moves (mv) the vertical gap (vg) of SS to 0.1 mm. The SPEC command

mvr ssvo 0.1

moves relative (mvr) the vertical offset (vo) by 0.1 mm. The equivalents in horizontal are of course named hg and ho. The command

wss

will display the current settings of the slit.

Tranfocator

Transocator is filled with the beryllium compound refractive lenses (CRLs) and is used to focuse the beam at the desired position in the energy range 7-30 keV. Can only be operated by the beamline staff. This device is normally not touched during an experiment.

Photon absorbers

Can only be operated by the beamline staff. This device is normally not touched during an experiment.

OH1 Beam shutter

The OH1 beam shutter allows you to enter the experimental hutch EH1 without being irradiated (very convenient) and is a main part of the personnel safety system (PSS) at the beamline. The beam shutter is operated by SPEC with the self-explanatory commands "shclose" and "shopen". The hutch door is locked automatically before the shutter can be opened. This safety procedure you will learn more about in the mandatory SAFETY TRAINING for users.

CRLs

Additional set of CRLs are installed in OH3 optic-hutch for stronger focusion option. CRLs focuse 7, 8.1 and 9.5 keV in the EH2 experimental hutch. They are operated by the beamline staff.

TS slits

Same as SS slits (see above). The TS slits are the last components before the beam meets the OH3 monochromator, approximately 56 meters from the undulator source.

OH3 monochromator

TheOH3 monochromator is a water-cooled Si(111) pseudo channel-cut monochromator operating in vertical scattering geometry. The crystal can provide 7-24 keV radiationi. This is done in SPEC by typing

moveE 8.1

which will rotate the monochromator to 14.5 degrees. This means that the white beam hits the crystal surface under an angle of 14.5 degrees and consequently monochromatic radiation will be diffracted according to Bragg’s law. Find more details in Beamline Description (The EH2 Monochromator). This monocromator delivers monochromatic beam to the experiments carried out in the EH2 expeimental hutch (EH2).

OH3 beam shutter

The OH3 beamshutter approximately 57.5 m from the beam may be operated by the "optics" commands

shopen 2

and

shclose 2

This allows access to the EH2 experimental hutch. The shutter in the OH1 experimental hutch exit may also be operated (takes the beam off the OH3 mono) with

shopen 0

and

shclose 0