Proposal preparation for the HED instrument

Call for Proposals - Frequently asked Questions and Answers

Q: Where can I find the available parameters that HED offers for the current call for proposals?
A: Please refer to this    pdf-document    (also found in the subcategory "Documentation" on this website).

 

Q: How many experiments will be scheduled?
A: For the second half of 2021, we can schedule between 4 and 8 user experiments between end of July and mid-November 2021. Time to change the setup between those may be 1 week, but sometimes only 1-2 days.

 

Q: What target chambers are available?
A: We offer both interaction chamber 1 (IC) and interaction chamber 2 (IC2). The vacuum in both chambers is oil-free and base operation pressures are around 10-4 mbar (however the chamber can reach lower pressures). Please ask us for our vacuum guidlines.
IC1 offers a rectangular multi-purpose chamber with a breadboard. The sample stack in located in the center, featuring a rotation stage, a large hexapod and a sample scanner.  A vertical breadboard has in-vaccum motorozed rails, where detectors and spectrometers can be mounted. The radius of curvature of these rails points towards the interaction point.
IC2 is a chamber dedicated to precision x-ray diffraction. In 2021, it will offer a Diamond Anvil Cell platform. Note that the 1M AGIPD detector is not yet available, however you can approach us if you are interested in using the AGIPD mini-half, which is an intermediate solution.

 

Q: Will there be a bunchtrain-resolved detector (kHz, MHz) available?

Yes - While the timeline to finalze the 1M AGIPD detector into the HED instrument does not allow to use this detector in 2021, we have implemented a smaller, in-air version, the so-called AGIPD mini-half. Please contact the instrument scientists for more details. The development of "burst mode" for the JUNGFRAU detector is ongoing (200 kHz) and is also not.

 

Q: What x-ray photon energies and tunability do you offer?
A: We offer full tunability between 5 and 24 keV with SASE spectrum (0.2% bw). We will have all monochromators available (1eV bandwidth 5-18 keV, and 40 meV bw at 7.49 keV). We offer focused x-rays or collimated x-rays with < 2 µrad divergence and few 100 µm diameter. Currently, we have demonstrated pulse energies in SASE2 of 2.5 mJ at < 10 keV, less for higher photon energies. Seeding will be available in 2021 as a special mode between 8 and 14 keV.

 

Q: Will variable pulse duration (2-100 fs) be available for this run?
A: No, we will not offer this yet to users, this scheme needs development and diagnostics.The linear accelerator is currently running with 250 pC electron bunch charge, and this will probably continue for a while. The SASE intensity is about 1-2 mJ, and the x-ray pulse length is estimated to be 25 fs maximum. It is probably even a bit shorter, because not the entire electron bunch is lasing. In future (not this call for proposals), it will be possible to have shorter pulses (down to single fs) with less intensity by shortening the electron bunch.

 

Q: Can I bring my own instrumentation (motors, stages, cameras) and will you implement them into the XFEL control system?
A: In general no. We will be still occupied to commision the baseline instrumentation at HED, and we have limited resources to implement additional features. We ask you to use the available equipment. Also, since there are only a few days between two experimental campaigns, there is very little time to work on the mechanical setup. The only possibility is to bring a fully prealigned setup with independent motor controls, which runs stand-alone for your experiment, but this is not perferred as the data is not synchronized with the bunch ID pattern.

The High Energy Density (HED) scientific instrument is a new, unique platform for experiments combining hard X-ray FEL radiation and the capability to generate matter under extreme conditions of pressure, temperature or electric field using the FEL, high energy optical lasers, or pulsed magnets.

Scientific applications will be studies of matter occurring inside exoplanets, of new extreme-pressure phases and solid-density plasmas, and of structural phase transitions of complex solids in high magnetic fields. The first user experiment took place in May 2019. We have meanwhile commissioned several additional capabilities, such as focusing, spectrometers, monochromators, sample environments. The HIBEF user consortium has contributed a second target chamber, a diamond anvil cell platform, the RE.LA.X and DiPOLE laser systems, and a laser-shock platform.