Since the re-start in August 2025, the superconducting linear accelerator of the FLASH facilities provides electron bunches with up to 1.35 GeV energy for the two independently operating undulator lines. The FLASH1 line is in the commissioning process for full external seeding with the full repetition rate that FLASH can provide in burst mode. More information on the FLASH2020+ upgrade can be found here.
FLASH1
The new undulator chain of FLASH1 consists of two modulator and six radiator undulators. The former are planar devices with a long period of 84mm, while the latter are based on the APPLE- III design with 35mm period. In order to increase the pulse energy at short wavelengths, three refurbished U32 devices from the former sFLASH experiment have been installed between modulators and radiators. They have a variable gap and are are identical to the U32 undulators used at PETRA III.
The parameters of the FLASH1 undulators are listed below:
|
Modulator |
U32 |
Radiator |
|
|---|---|---|---|
|
minimum magnetic gap (mm) |
9.0 |
9.0 |
8.0 |
|
period length λU (mm) |
84 |
31.4 |
35 |
|
device length L (m) |
2.5 |
2.0 |
2.5 |
|
number of full periods |
27 |
61 |
70 |
|
deflection parameter Kmax |
10.6 |
2.7 |
3.9 |
|
number of devices |
2 |
3 |
6 |
|
peak field Bmax (T) |
1.4 |
1 |
1.2 |
|
max. magnetic load F (kN) |
29.4 |
5 (force compensation) |
FLASH2
The second branch FLASH2 contains 12 planar U32 variable gap undulators with a maximum deflection parameter Kmax = 2.81 and 2.5 m length each. In addition, FLASH2 is equipped with a Laserheater and an APPLE3 type afterburner.
The parameters for the FLASH 2 undulators are listed in the table below.
|
ID parameters |
U32 |
Apple3 |
|---|---|---|
|
minimum magnetic gap (mm) |
9.0 |
8.0 |
|
period length λU (mm) |
31.4 |
17.5 |
|
device length L (m) |
2.5 |
2.5 |
|
number of full periods |
77 |
|
|
deflection parameter Kmax |
2.81 |
0.95 |
|
number of devices |
12 |
1 |
|
peak field B0 (T) |
0.98 |
0.56 |
|
max. magnetic load Fmag (kN) |
15 |
Further literature:
Rönsch-Schulenburg, J. ; Braune, M.; Brenner-Abild, G.; Dziarzhytski, S.; Götze, K.; Kuhlmann, M.; Niknejadi, P.; Schaper, L.; Schneidmiller, E. A.; Schoeps, A.; Tischer, M.; Vagin, P.; Vogt, M.; Zemella, J., "Operation of the variable polarization undulator on the third harmonic of a SASE FEL", X-Ray Free-Electron Lasers: Advances in Source Development and Instrumentation VII, Prague, Czech Republic, 7 Apr 2025 - 11 Apr 2025 Proceedings of SPIE 13536, 1353604 (2025) [10.1117/12.3058405]
Construction and commissioning of an APPLE-III afterburner undulator as a prototype for radiators in the new seeding line of FLASH2020+", J. Phys.: Conf. Ser. 3010 012045 (2025) [10.1088/1742-6596/3010/1/012045]
