DEIMOS

The buffer chamber and the DiagOn (for Diagnostic Onduleur) are located in the radiation-protection hutch.

The pink beam emitted by the undulators can be visualized and characterized using the DiagOn device (diagnostic tool intended to precisely define the emission axis of the undulator [1].

Also located in the radiation-protection hutch, the first optics chamber (a.k.a. M1 chamber) serves basically to remove the unwanted beams : higher harmonic rejection, heat load, Bremsstrahlung…

It contains 3 mirrors that are water cooled : first a plane mirror (Pt coated SiC-CVD), that dissipates a large part of the 160W in-coming power, followed by two toroidal mirrors (Pt coated Si and Rh coated Si) to choose from which focus the beam into the monochromator.

The monochromator is equipped with two plane gratings which are respectively a variable groove depth (VGD) grating with 1600 lines/mm, and a Mo₂C/B₄C alternate multilayer (AML) grating with 2400 lines/mm. The VGD grating is optimized for the energy range 240-1500 eV while the AML grating is optimized for the energy domain 1000-2500 eV.

With the VGD grating the monochromator is usually operated in the Petersen geometry with a fixed c factor that can be choose to either maximize the flux with a poor resolution (large value) or minimize the flux with an improve resolution (small value down to 0.04). The energy resolution is further defined by the opening of the exit slits located 4m downstream of the main UHV vessel. The ultimate resolving power (exit slits closed) is around 30000 for a factor c of 0.2.

The last optical stage is a simplified Wolter mirror combination associating a spherical mirror and a toroidal mirror. The choice between 2 spherical mirrors and 2 toroidal mirrors allows for 2 spot sizes ~80×80 mm² and ~800×800 mm² for the 2 working points (associate to the 2 workstations).

Two end-stations are available on DEIMOS :

• A superconducting magnet (CroMag) providing ±7 T along the x-rays beam or ±2 T perpendicular to the beam. A variable temperature insert (V²TI) has been developed for temperatures in the 1.5-350 K range. A new dilution insert is in development to go in the ultra low temperature range and is intended to cover the 0.2-350 K temperature range [2].
• A 2T electromagnet (MagneTwo) allowing for a fast flipping of the magnetic field up to 1Hz. This end-station host several dedicated inserts: a high temperature insert (20-1000 K), an insert with multiple electrical connections (V²TI) (allowing for instance operando studies by applying voltages on a sample) [3] and a microfluidic insert for the studies of liquids.

You will find below the informations concerning the endstations :

Here are three different types of inserts :

[1] T. Moreno, E. Otero, P. Ohresser, "In situ characterization of undulator magnetic fields", Journal of Synchrotron Radiation 19(2): 179-184 (2012)

[2] Joly, L., Muller, B., Sternitzky, E., Faullumel, J. G., Boulard, A., Otero, E., Choueikani, F., Kappler, J. P., Studniarek, M., Bowen, M. and Ohresser, P., "Versatile variable temperature insert at the DEIMOS beamline for in situ electrical transport measurements", Journal of Synchrotron Radiation, 2016, 23 (3): 652-657.

[3] J.-P. Kappler, E. Otero, W. Li, L. Joly, G. Schmerber, B. Muller, F. Scheurer, F. Leduc, B. Gobaut, L. Poggini, G. Serrano, F. Choueikani, E. Lhotel, A. Cornia, R. Sessoli, M. Mannini, M.-A. Arrio, Ph. Sainctavit, and P. Ohresser, "Ultralow-temperature device dedicated to soft X-ray magnetic circular dichroism experiments", Journal of Synchrotron Radiation, 25(6): 1727-1735. (2018)

Connected to the end-station, there are several equipment allowing for the introduction and the preparation of the samples :

• A fast load-lock is used to transfer sample in the UHV environment common to both endstations. The load-lock can be connected to a glove box (6) allowing a transfer through inert atmosphere. Beside, the use of a UHV suit case is also possible to transport sample from a nearby laboratory to our set-up. Contact your local contact if you whish to use DEIMOS’s suitcase.
• The "MBE" chamber is hosting several UHV equipment for in situ sample characterization and preparation :
  • Sample preparation :
    • Ion sputtering,
    • Omniax manipulator with a temperature range of 150-700K,
  • Evaporation (also possible on the small side chamber Raoul-petite) :
    • 2 Knudsen cells,
    • 2 effusion cells for organics (5),
    • 3 electrons beam evaporators (Omicron EFM-3 and EFM-3T) (3),
    • Quartz microbalance,
  • Sample characterization :
    • Auger analyser (4),
    • LEED (Low Energy Electron Diffraction) (2),
    • Variable temperature STM (50-500K) (1).

We can analyze most of solid samples: deposited on substrates or on single crystals, transparent, powder, etc... The samples can be prepared at users’ institute or directly on the beamline using our MBE vessel and other ancillary equipment (pdf).

CroMag :

We are using mainly 2 standards as sample holders : Omicron type plates and our copper block.
The samples can be fixed directly on the copper blocks ( click here for the schematic of a sample holder ) and held by copper masks (see figure a-c) made-to-measure; maximum sample size 9x25mm².

The samples can also be assembled on Omicron type plates  (pdf) available on DEIMOS, and can be held in place by wires, welded tabs, or screws. It is also possible to use our thickened plates; maximum sample size 10mm diameter (see figure d).

We also have a rotating sample holder (see figure e); maximum sample size 9x9mm².

MagneTwo :

In MagneTwo, for measurements with the MilleK insert, samples must be mounted on Omicron type plates, for the V²TI insert requiring electrical contacts, samples are installed on electronic chips clipped on a dedicated copper block (see figure g), and for the microfluidic insert we use microfluidic chips (see figure i).

To insert the samples prepared ex situ, one usually uses the fast load lock (sas in French) (see photo below), or through the glove box (under inert atmosphere). It is also possible to use a UHV suitcase that can be connected to the sas via an intermediate pumping chamber (see photos below).

The parking slot of our UHV suitcase can host up to 6 Omicron type plates (limited to 3 for thick samples) (see photo).

Contact your local contact for more information about the use of the DEIMOS UHV case. Click here for supplier information.

On DEIMOS the interface to control the beamline is using scripting based on the PyTango biding [1]. With a small list of commands, it is possible to launch "macro" consisting of a series of actions/commands (launching scans, moving actuators, …) written in Python in a text file easy to edit and modify.

Acquisition usually mostly consists in cumulating absorption spectra (performed at dedicated sample conditions and polarization) and magnetization curves.

There is 2 ways to record absorption spectra and the resulting dichroic spectra:

• turboscan: the turboscan is a continuous scan (or scan-on-the-fly) where the 2 rotations of the gratings and mirrors (both in the monochromators) are moved to cover the energy range of interest while at the same time the energy (gap) and polarization (phase) of the undulator is enslaved to the monochromator energy trajectory [2]. During these displacements the sensors, and actuators positions are synchronously recorded. This method allows for shorter acquisition time (no dead-times) and smoother data acquisition because there is only one single displacement. A typical turboscan (80eV wide) is obtained in 2-3 min. For a dichroic spectrum one needs at least 2 XAS but depending on the statistic and to cancel instrumental artefact it is usually mandatory to record many pairs.
• flipscan: the flipscan is a step-by-step scan where the light polarization (CR / CL, for circular right / left) (using the undulator EMPHU) or the magnetization (+H / -H) (2T electromagnet) is flipped at each point in energy. The step-by-step flipscan is typically 30-40 min long but is very powerful to resolve very small XMCD signals.

Similarly, there is 2 ways to measure magnetization curves:

• turbohyst: the sensors are synchronously recorded while the magnetic field is performing the desired trajectory in magnetic field. A complete magnetization curve is obtained by recording 2 turbohyst for the polarizations CR and CL with the energy set at the maximum of the XMCD signal. The total time requested is typically around 45 min (depends highly in the trajectory in field).
• fliphyst: the fliphyst is a step-by-step scan where the light polarization (CR / CL) (using the undulator EMPHU) is flipped at each point in magnetic field. The step-by-step fliphyst takes more time compared to the turbohyst but allows to resolve signal that are not easily measured with the later.

[1] PyTango documentation website.

[2] Joly, L., Otero, E., Choueikani, F., Marteau, F., Chapuis, L., & Ohresser, P., "Fast continuous energy scan with dynamic coupling of the monochromator and undulator at the DEIMOS beamline", Journal of Synchrotron Radiation, 2014, 21(3): 502–506

Philippe OHRESSER, Beamline Manager : 01 69 35 96 82, philippe.ohresser@synchrotron-soleil.fr

Phone number of the beamline DEIMOS : 01 69 35 81 51 ; 01 69 35 81 52

Adress for shipping goods :
Synchrotron SOLEIL
L'Orme des Merisiers
Departementale 128
91190 SAINT-AUBIN
FRANCE