Time Resolved Experiment Beamline handbook

General Description:

This handbook lists a series of entries, that address keywords, that are important for performing time-resolved experiments. The links will guide you to the specific pages. Please note that this page is under permanent upgrade and feedback from users is very desirable.

Index:

A - C

• • absorber: The beamline is equipped with three set of absorbers in front of all optical elements, which allow inserting foils of carbon, diamond, aluminum and copper from 0.1 mm to 1 mm.
  • bunch length: The burst length (time resolution) of the x-ray beam is a function of the current of the electron bunch in the ring. It varies from 50 ps to 200 ps and can be seen in this picture.
  • bunch modes: The ESRF provides different filling patterns for the electron bunches that affect the available flux and the time structure of the x-rays. A sketch displayes the different patterns with their specific properties. More information is available for the machine group pages.
  • chopper: The x-ray pulse trains, that arrive from the torage ring with a MHz rate are diluted by a mechanical chopper, that is running at 896 Hz to extract  pulse trains with this frequency as well as single x-ray pulses with the aid of the heatload shutter and millisecond shutter.
  • cabling: The list of the motor cablings and the coaxial feedthroughs are available on the Laue workstation at the beamline (overview).

D - F
 

• • data storage: Please consult the ESRF pages about data storage and transfer policy on NICE. Typical runs with the MarCCD can give you several tens of Gigabyte, so be prepared (NB: These files can be effectively compressed). We can provide drives for CD burning (R/RW), DVD (4.7 and 9.4 GB), ZIP (100 MB), DAT (eg. 2GB) and pencils.
  • delay generators: A set of 3 (in the control hutch) Stanford delay generators are used to trigger different electronical elements of the beamline at 900 Hz, 10 Hz and in single shot mode.
  • detectors A set of different detectors can be chosen according to the needs of spacial and/or time resolution and detection efficiency.
  • diodes:
  • excitation: see different possibilities of the laser excitation of the sample: parallel to the x-ray beam or perpendicular to the x-ray beam.
  • femtosecond laser: For ultrafast excitation of the samples a femtosecond laser system based on a TiSa oscillator with regenerative flashlamp pumped amplification is used to produce 100 fs long pulses from 267 to 800 nm.
  • fluorescence calibration: 2D detectors such as the MarCCD can be calibrated in response by a fluorescence exposure, eg. a Sr excitation below and above the K-edge.
  • flux measurement: The flux of the x-ray beam can be measured at different positions along the beam path, where the signal on photodiodes is normalized by spec to x-ray photon numbers. A I0 monitor after the defining sample slits is currently in a test phase.

G - I
 

• • gas detector: A 0D gas detector filled eg. with Xe or Ar gas mixture allows the recording of scattered intensity in order to benefit from lock-in techniques.
  • goniometer: The sample goniometer is optimized for macromolecular crystallography (monochromatic or white beam mode), but allows a range of different setups.
  • goniometer head: Manual goniometr heads are used to position the sample in the beams and center of rotation.
  • heatload shutter: The heatload shutter cuts the x-ray beam in the required frequency for the experiment to prevent excess heatload of the x-ray source from deforming the optical elements.
  • internal files: At the workstation LAUE a number of help pages can be found for use at the beamline.

J - L

• • laser: The time resoled beamline is currently equipped with two pulsed laser sources: a transportable nanosecond laser and a permanently installed femtosecond laser.

M - O

• • MarCCD: Twodimensional detector to collect Bragg spots (Laue method, oscillation method) of single crystals, Debye-Scherrer rings of powder samples, diffuse scattering from liquid solutions. The x-ray active scintillator consists of a 40 mum thick Gd2O2S:Tb plate of 133 mm diameter, the scintillation light is guided via fiber optic taper to a cooled (-70 C) CCD chip with 2048x2048 pixels. The effective pixel size of the camera is 64.689 mum and the point spread function 1.5 pixel at FWHM.
  • monochromator: currently a silicon Bragg-Bragg monochromator with (111) orientation is used.
  • microscope: positioning of the sample is watched with a long working distance microscope equipped with colour CCD camera.
  • millisecond shutter: see shutters
  • mirrors: two mirrors are placed in the optics hutch: a plane mirror for the high pressure experiments and a toroidal mirror for the time resolved experiments
  • nanosecond laser: A nanosecond modular laser systm is commisioned for studying relaxations at longer timescales than 5 ns.
  • network connection: Two ID's for networking a PC can be provided at workgroup ID09 (see internal pages).
  • orthogonal excitation:
  • oscilloscope: A fast sampling oscilloscope is used for recording the time structure of laser and x-ray beam. It is remotely controlled on a PC. A second oscilloscope in the control hutch can be used for the analysing the response of different detectors and electronics.

P - R

• • parallel excitation: For a colinear excitation of the sample a mirror system guides the laser to tha sample with a minimal angle of 20 degrees with respect to the x-ray beam.
  • photodiodes: see detectors
  • plane mirror: The plane mirror is used for the high pressure exeriments and allows a vertical focussing (large radius along the x-ray path).
  • pipe: A thin pipe of 300 mm length with a variable tip at the exit is used for cleaning the x-ray beam from diffuse scattering and flushing the path with nitrogen or helium.

S - U

• • shutters: Two shutters and a chopper provide the required time structure of the x-ray pulses for stroboscopic to single shot  exposures of the sample.
  • spot size: The x-ray spot size at the same is about 250 x 250 mm.
  • streak camera: allows a temporal of the scattering distribution below 1 ps,  see streak camera pages.
  • timing detector: A GaAs photoconductor is used for the measureement of the time delay between laser and x-ray pulse.
  • toroidal mirror: The toroidal mirror is used for focussing the x-ray beam in vertical direction (large radius along the x-ray path) and horizontal direction (small radius perpendicular to the beampath).
  • slits: A set of 4-blade slits defines the x-ray path within the optics, the sample slits consist of a Risoe slit of 4 independant blades.

V - Z

• • wire monitors: Two sets of wire monitors are available to track the position and shape of the x-ray beam. In the optics hutch a pair can pick up the mirror reflection (for experts) and in the Laue hutch one pair watches the correct position for entering the experiment (for users).
  • x-ray properties of materials: why not consult the Berkeley server.