DESY (Deutsches Elektronen-Synchrotron): Facilities and User Access

DESY (Deutsches Elektronen-Synchrotron) is a German national research centre for accelerators, photon science, particle physics and astroparticle physics, based in Hamburg and Zeuthen and a member of the Helmholtz Association. It is best known to researchers outside physics as an operator of X-ray light sources, chiefly PETRA III and FLASH, that external scientists can use by submitting a proposal.

Short answer: what DESY is and why it comes up in lab work

DESY was founded on 18 December 1959 in Hamburg and now works at two sites, Hamburg and Zeuthen in Brandenburg. It is not a single instrument. It is an organisation that runs several accelerator-based facilities and hosts partner institutes. For a lab group, the practical meaning is access: DESY’s photon facilities provide intense X-ray and ultraviolet light for experiments such as protein crystal structure determination, studies of welding seams and metal alloys, nanotechnology and medical research. For a research office, the practical meaning is a large, publicly funded national centre with an international user community, comparable in role to the Advanced Photon Source in the United States.

Definition and scope

DESY describes itself as a Helmholtz Association research centre. Its own figures, as published on its about page (read 2026-11-13), are:

• About 3,000 employees, including roughly 1,300 scientists, plus more than 130 trainees.
• Around 500 doctoral students and postdoctoral researchers.
• More than 3,000 guest scientists from over 40 countries each year.
• A basic budget of 349 million euros, of which 320 million euros is attributed to Hamburg and 29 million euros to Zeuthen.
• Four research areas: accelerators, photon science, particle physics and astroparticle physics.

The name is historical: PETRA III, for example, descends from the PETRA ring commissioned in 1978 and later converted into an X-ray source, and FLASH ran as a test facility from 1992 to 2005 before becoming a user facility. The facilities that users book today are therefore the product of repeated conversion and expansion rather than of a single construction project.

How researchers use DESY facilities

External researchers normally reach DESY’s photon facilities through the Photon Science user area. The page lists three connected functions in one portal, called DOOR: user registration, proposal submission, and administration of the experiment. The same page has a “Calls and Deadlines” section and names a Photon Science User Office at DESY, so the sequence is registration first, then a proposal answered to a call, then administrative follow-up once beamtime is allocated.

Two points about what this means in practice, both stated by the user pages:

• PETRA III and FLASH are the two photon facilities that DESY itself operates for users.
• The European XFEL, CFEL (Center for Free-Electron Laser Science) and CSSB (Centre for Structural Systems Biology) are named as partners rather than as parts of the DESY user programme.

The user pages do not state fees, review criteria or deadlines in the section read, so those details should be taken from the current call itself rather than assumed from another facility. The user area frames access as a proposal submitted to a call, so a research office should treat a DESY visit as a proposal-driven activity with its own administration step, not as an off-the-shelf service order.

Facilities compared

The data table below the article sets out what DESY states about its main facilities. The summary here explains how to read it.

PETRA III

PETRA III is a storage-ring X-ray source with a ring length of 2,304 metres. It began as PETRA, commissioned in 1978, and was converted into an X-ray source. DESY states that since 2010 it has been one of the brightest storage-ring-based X-ray radiation sources. It offers 25 beamlines with almost 60 instruments. Its listed uses include protein crystal structure, welding seams and metal alloys, nanotechnology and medical research.

FLASH

FLASH is a free-electron laser built on a superconducting linear accelerator using TESLA technology. DESY describes it as the world’s first free-electron laser in the X-ray range, working in the vacuum ultraviolet and soft X-ray range using self-amplified spontaneous emission (SASE). It ran as a test facility from 1992 to 2005 and has been a user facility since 2005. It is 315 metres long, serves two beamlines in parallel, has five experimental stations in the Albert Einstein hall, and has room for six more in the Kai Siegbahn hall. DESY states that the expansion more than doubled user capacity.

PETRA IV

PETRA IV is a planned successor project. DESY’s about page describes it as a “4D X-ray microscope”. It is a plan, not a running facility, and it should not be described to funders or collaborators as available.

European XFEL

The European XFEL is a separate facility in which DESY is the main shareholder. It runs its own user office and its own proposal system. A joint DESY and European XFEL users’ meeting took place from 27 to 29 January 2026 with more than 1,100 registered participants, which shows how closely the two user communities overlap, but a proposal to one is not a proposal to the other.

Where it matters for labs and research offices

Funding structure

DESY states that about 90 percent of its basic funding comes from the national level, specifically the Federal Ministry of Research, Technology and Space, and about 10 percent from the states of Hamburg and Brandenburg. For research administrators, this explains why DESY is usually described as a national facility rather than a university service, and why DESY reports guest scientists from more than 40 countries each year. How much of this applies to cost recovery for a particular visiting group is not given in the sources and must be confirmed with the facility.

Scale of use

DESY reported that in 2019 nearly 3,400 scientists from more than 40 countries used PETRA III and FLASH. That figure is a useful order-of-magnitude reference for the size of the user community, though it describes a single year and should be dated if quoted.

Planning around beamtime

Because access runs through calls and deadlines, a group that needs measurements from structures, alloys or nanomaterials should treat the call calendar as part of project planning. Sample preparation work, such as growing protein crystals, belongs in the home lab, which is why DESY-linked work often connects to ordinary bench topics. Readers new to the underlying method can start with what is crystallography and what is biophysics. Another national research centre with a comparable role in its own country is described in the RIKEN guide.

Common misunderstandings

• DESY is one machine. It is an organisation with several facilities, and the sections above show that PETRA III and FLASH differ in design, scale and typical use.
• DESY and the European XFEL are the same. DESY is the main shareholder in the European XFEL, but the European XFEL has its own user office and proposal system.
• DESY is only for particle physics. Particle physics is one of four research areas, alongside accelerators, photon science and astroparticle physics, and the photon facilities have their own dedicated user office.
• DESY is a university. It is a Helmholtz Association centre funded predominantly by the federal level.
• PETRA IV is operating. It is a planned project.
• The abbreviation points to a brand. Search results for the bare term “desy” can include unrelated products and companies; this page concerns the Hamburg and Zeuthen research centre only.

FAQ

What does DESY stand for?

Deutsches Elektronen-Synchrotron, German for German Electron Synchrotron.

Where is DESY located?

At two sites, Hamburg and Zeuthen in Brandenburg, Germany. The Hamburg site carries most of the budget: 320 of the 349 million euros basic budget in DESY’s own figures.

How do outside researchers get beamtime?

They register and submit a proposal through the DOOR portal of the DESY Photon Science user area, which also handles administration of the experiment. Calls and deadlines are published in that area. Proposals to the European XFEL go through that facility’s separate system.

Who funds DESY?

About 90 percent of the basic budget is national (Federal Ministry of Research, Technology and Space) and about 10 percent comes from Hamburg and Brandenburg.

What is the difference between PETRA III and FLASH?

PETRA III is a 2,304 metre storage ring serving 25 beamlines with almost 60 instruments; FLASH is a 315 metre free-electron laser linac in the vacuum ultraviolet and soft X-ray range that serves two beamlines in parallel.

Sources

• DESY, About DESY (read 2026-11-13).
• DESY, PETRA III (read 2026-11-13).
• DESY, FLASH (read 2026-11-13).
• DESY Photon Science, Users’ area (read 2026-11-13).
• DESY Photon Science news, users’ meetings of DESY and European XFEL (read 2026-11-13).