Beamtime hacks

Tips for designing an optimal measurement plan

Below are a list of considerations. It’s non-exhaustive. As development work is ongoing, some of these considerations may be outdated. Consult with your local contact.

  • Multi-hour, automated overnight measurements with the beamline may be infeasible, due to heat-induced deformation of the M1 mirror (need to periodically re-tune M1 pitch, etc.). The measurements could be semi-automated, if a user periodically stops by the hutch.

  • Unless the surface is ultra-clean, chemical mapping with XAS-PEEM is preferred to XPEEM, as the yield of secondary electrons is expected to be higher versus primary photoelectrons

  • The continuous application of a high voltage between the microscope objective and sample surface generally leads to carbon deposition - periodic surface regeneration may be needed

  • Scangui (ascan macro) enables most beamline and microscope parameters to be swept –> automated scans

  • Five slots exist in the storage chamber attached to the main chamber, though 2-4 slots are typically occupied. Talk to your local contact about storing sample(s) inside.

  • Micro-ARPES typically works well with photon energies up to ~100 eV. The photon flux decreases above 100 eV for the 1200 lines/mm grating, plus the photoionization cross-sections decrease with increasing photon energy.

  • The beamline elements are contaminated with carbon, yielding lower-than-expected photon flux at energies at and near the carbon K-edge

  • The beamline lacks proper i0-type normalization, needed for generating high-quality X-ray absorption spectra. A gold mesh exists upstream of the M4 mirror, but the mesh is dirty and we cannot deposit fresh gold onto it.

  • When XAS measurements are desired, check the literature (and/or use Google Image search) to determine if the edge has been measured before - having a core level doesn’t mean you have an absorption edge

Tips for operating the beamline

  • Track the beamline flux by periodically inserting the photodiode into the beam path; tuning the pitch of the M1 mirror is usually sufficient to maximize the flux.

  • The spot size at the sample position is around 15 um (H) x 15 um (V) with a 0.15 mm exit slit opening in the vertical and horizontal directions (the image at the exit slit is demagnified by a factor of 10 at the sample position).

  • Peak photon flux is obtained at ~100 eV (for the 1200 lines/mm and 300 lines/mm gratings)

Toilets and water/tea/coffee stations

Tea, coffee, hot chocolate, etc. are available for free, 24/7. The approximate locations of the drink stations and toilets are displayed in the schematic layout of the Lab.

_images/lab_schematic_toilets_water.png

Figure 1. Schematic of MAX IV, showing the toilets and drink stations that are easily accessible from MAXPEEM.

WiFi

  • maxiv_user (log in with MAX IV DUO username and password)

  • maxiv_visitors (intended for 1 day users, Internet access only, receive a token through your email address)

  • eduroam (Internet access only)

  • maxiv_staff (not applicable to users)

For more details on access privileges, etc. see https://www.maxiv.lu.se/beamlines-accelerators/controls-it/it-services/wifi/

Food options

In short, the main options are: * visiting food trucks (usually located close to the main entrance, where the reception is, from 11-13 Monday - Friday); call Reception (+46462229872) for the latest schedule. * cooking in the user kitchen at MAX IV and/or in the guestrooms at Forskarhotellet * microwaving frozen food purchased from the vending machines * ordering food delivery (e.g. foodora.se) * stationary food truck “Dagens lunch 60” serving burgers and daily specials (5 minute talk from the Lab, Odarslövsvägen 50)

See https://blochdocs.maxiv.lu.se/food.html for more details.

Resting and exercise rooms

A sleeping room is available in the basement of the E-building. First come, first served. An exercise room, equipped with a pull-up bar, bench, weights and cardio training machines, is also available in the basement.

Tools and supplies available in the MAXPEEM prep lab

  • Hand tools: tweezers, pliers, screwdrivers, wrenches, etc.

  • Vacuum parts

  • Kapton tape

  • Dessicator

  • Optical microscope

EPO-TEK epoxies, pastes, etc. stored in the D3 chemical lab (fridge). Ask if you need something special.