Experimental Hutch

last modified 14-10-2008 16:27

The experimental hutch is the safety hutch where the experiment will take place. Because of the strong X-ray beam, this hutch is automatically locked during operation for safety reasons. The hutch must be searched and closed before the beam is available. This procedure is the main topic of the SAFETY TRAINING COURSE that must be followed by all ESRF users prior to the start of their experiment.

At ID10A there are two experimental hutches, TROIKA I and TROIKA III served by two different monochromators. They are described in the Machine and Optics hutch section. The main component of an experimental hutch is the diffractometer, including various motorized translations and rotations to be able to control your experiment.

All motor names are controlled by spec, the beamline operations system which is running on the tina.esrf.fr/tinc.esrf.fr (TROIKA I/III) unix workstations. Usually the spec version used is sixc (sixcircle) and it can be started simply by typing "sixc" in a UNIX prompt. (A spec guide is available).

The TROIKA I Diffractometer

The TROIKA I diffractometer is described in the Beamline Description (TROIKA I Instrumentation). The local contact will align the beamline and diffractometer for you at the beginning of the experiment. The diffractometer has about 40 motors that can be operated independently from SIXC, here we will only describe the most commonly used ones. For more details ask your local contact.

TROIKA I Motors

All diffractometer motors can be moved by the spec command

mv motorname x

This moves (mv) the motor to the position x. motorname is often a two or three letter name. The units of x is mm for translational motors while it is degrees for rotations. The sign of the motors follows a right hand coordinate system where the x-axis is along the beam direction and the z-axis is vertical, positive up (deviations from this rule unfortunately exists). The command "mvr" will move relative to the current motorposition. The motorposition is displayed by typing

wm motorname

Here follows a description of the most important motors of the TROIKA I diffractometer and their functions.

Motorname	Function
ttm	Means two-theta monochromator. It is used to center the diffractometer on the monochromatic beam coming from the monochromator. ttm is defined relative to the direct beam and so if the theta angle of the mono is 14.5, ttm should be 29 degrees. ttm moves the whole diffractometer on air cushions so it is important to check that there’re no obstacles on the floor before moving ttm. The air cushions can be manually swithhed on/off with the SPEC commands "airpad_on" and "airpad_off"
z0, z1 and z2	Height of the three towers (elevator stages) of the diffractometer. These towers carry beam pipes (X95 aluminum flight paths) with attenuators, detectors and a local mirror by which higher order X-rays can be suppressed. The beam pipes are filled with Helium.
r0, r1 and r2	Rotation of the above mentioned beam pipes.
fx and fz	horizontal and vertical translation of the pinhole stage. The pinhole stage consists of a 80 mu gold foil where holes have been etched into. The smallest pinholes are 4mu and 12mu and are used to define the beamsize in coherent scattering experiments.
fgh, fgv, gh, gv	Control of the guard slit. fgh and fgv are the horizontal- and vertical gaps while gh and gv are the horizontal and vertical offsets. The guard slit is used to suppress Fraunhofer diffraction from the pinholes.
th	This is the rotation of the sample table which is a standard Huber goniometer head.
phi and chi	Tilts of the goniometer head
xs and ys	Horizontal translations of the goniometer perpendicular and parallel to the beam
zs	Vertical translation of the goniometer
z3 and r3	Height and rotation (in the vertical plane) of the flightpath carrying the detector stage. This flightpath is usually a standard X95 aluminum piece with length ranging from 0.5 m to 2m.
del	Rotation in the horizontal plane of the flight path carrying the detector.
rgh and rgv	horizontal- and vertical gap of the pre-detector slit
rx and rz	horizontal and vertical translation of the pre-detector slit.

Several other motors might be of interest depending on the actual experimental set-up.

A motor is controlled by SPEC through the dpap motor drives situated in the large blue racks in the control hutch. It is important NOT TO DISCONNECT ANY MOTOR CABLES without the dpap rack being switched off. In general, modifications of the motors and dpaps can only be carried out by the beamline staff.

Attenuators

Attenuators are installed before the pinhole stage at the elevator tower controlled by the motors z2 and r2. The attenuators are operated by the command "att x" where x is a number between 0 and 15. The command "att 0" takes out all attenuators. The status of the attenuator is displayed by typing "att" or by looking at the controller in the NIM rack. The attenuators consist of thin metal foils and is calibrated at 8keV so the attenuation roughly follows 10^x/2.

Monitor detector

A monitor detector is installed after the pinhole stage. This enables the measurement of the incident beam intensity by typing "ct". The monitor registers the photons scattered from a Kapton foil and the command "eff" calculates the scattering efficiency. The command "eff 8 40 1 0.08" will calculate the efficiency at 8 keV when the distance from the monitor to the Kapton foil is 40mm with a monitor aperture of 1mm and a Kapton foil thickness of 0.08 mm. Different apertures and Kapton foils are available at the beamline. For details about detectors in general, see below.

Detectors and Correlators

BICRON scintillator counter Model 1XM.040B, PMT type R580, with beryllium entrance window.

Crystal size: 1" x 1mm; PMT size: 1.5"; Energy range: 3 to 100 keV; Resolution: 30%; Count rate range: 0-30000 cts/sec.

Two types of CCD cameras are available : A deep depletion camera that is used in direct illumination mode to be able to do single photon counting for XPCS applications. In addition, a standard front-illuminated camera having a 1:1 lens system coupled with a thin phosphor screen for standard SAXS applications is available. Both CCDs are Princeton cameras with 1242 x 1152 pixels and a pixel size of 22.5 µm (availabilty of the direct illumination CCD camera is subject to prior collaboration agreement).

For X-ray Photon Correlation Spectroscopy (XPCS), two correlators are available:

1. Internal correlator: ALV5000\E, a multiple tau digital Correlator, for single or dual auto-correlation and cross-correlation, 200 ns sampling time and up to 288 Multiple Tau channels.

2. External correlator: Flex01D-08, fast high resolution multiple tau digital correlator, with 8ns minimum sample time and 1088 real time channels.

Helium

Some of the flightpaths are filled with He (from the big pressurized bottle at the wall). It is important to check the He flow from time to time.

Other Equipment at TROIKA I

The experimental hutch is equipped with a lot of additional hardware. Surely you will use different pumps(turbo/molecular pump or membrane pump) during your experiment but also other devices such as displex cryostats and a Small Angle X-ray Scattering(SAXS) chamber are available. For information about specialized equipment not described here, ask your local contact.

TROIKA III Experimental Hutch

The TROIKA III experimental hutch comprises an almost stationary setup optimized for coherent SAXS experiments. The main features are two granite tables with the optics and the diffractometer and an optical table carrying the detector assembly. More details about the TROIKA III station (includinc SPEC motornames) can be found in the Beamline Description (TROIKA III Station).