Conceptual Design of a Liquid Helium Vertical Test-Stand for 2m long Superconducting Undulator Coils

Superconducting Undulators (SCUs) can produce higher photon flux and cover a wider photon energy range compared to permanent magnet undulators (PMUs) with the same vacuum gap and period length. To build the know-how to implement superconducting undulators for future upgrades of the European XFEL facility, the test stand SUNDAE1 for the characterization of SCU is being developed. The purpose of SUNDAE1 is the training, tuning and development of new SCU coils by means of precise magnetic field measurements. The experimental setup will allow the characterization of magnets up to 2m in length. These magnets will be immersed in a Helium bath at 4K or 2K temperature. In this article, we describe the experimental setup and highlight its expected performances

SUNDAE1: A Liquid Helium Vertical Test-Stand for 2m Long Superconducting Undulator Coils

Superconducting Undulators (SCUs) can produce higher photon flux and cover a wider photon energy range compared to permanent magnet undulators (PMUs) with the same vacuum gap and period length. To build the know-how to implement superconducting undulators for future upgrades of the European XFEL facility, two magnetic measurement test stands named SUNDAE 1 and 2 (Superconducting UNDulAtor Experiment) are being developed. SUNDAE1 will facilitate research and development on magnet design thanks to the possibility of training new SCU coils and characterizing their magnetic field. The experimental setup will allow the characterization of magnets up to 2m in length. These magnets will be immersed in a Helium bath at 2K or 4K temperature. In this article, we describe the experimental setup and highlight its expected performances

A horizontal Brazil-nut effect and its reverse

Transport effects in a monolayer consisting of a binary granular mixture, confined in a horizontally vibrating circular dish, are studied experimentally and compared with a reduced theoretical model. Depending on the ratio of the particles' material density and size, migration of the larger particles occurs either towards the boundary or to the center of the circular container. These directed motions show similarities to the Brazil-nut effect and its reverse form

Summary and results of the cryoplant operation for HERA

For about 15 years, leptons and protons collided inside the HERA particle accelerator with the intension of investigating the protons’ inner structure. 646 superconductive electromagnets and 16 superconductive cavities had to be constantly surrounded by liquid helium to operate at a temperature of around 4 K. To ensure the helium supply of HERA’s superconductive components a highly productive refrigeration plant was built. In this paper we report on the experience gathered during nearly 20 years of operation of the refrigeration plants’ 3 cold boxes and the corresponding 14 screw compressors together with the helium distribution system and the purification system

RF Heat Load Compensation with Electrical Heaters for XFEL Accelerator–Measurements at CMTB, AMTF and FLASH

Since 2007, the European X-ray Free Electron Laser (XFEL) is being constructed at DESY, Germany. 800 superconducting niobium 1.3 GHz nine cell cavities and 100 superconducting magnet packages will be operated in a liquid helium II bath at 2K. The static and dynamic heat loads at 2K result in a vapour mass flow up to 96 g/s at 3100 Pa. A four stage cold compressor system is used to return the vapour to the XFEL helium refrigerator. Relative pressure oscillations of the helium II bath should be kept below 1% for stable RF operation of the cavities. In addition, fast changes of vapour pressure and mass flow at the inlet of the cold compressors must be avoided during variation of RF load, e.g. due to switching on/off of RF power or due to cavity quenches. Electrical heaters in the helium II bath of the XFEL linac will be used to compensate the RF load changes. The concept and results of measurements performed at Cryo Module Test Bench (CMTB), Accelerator Module Test Facility (AMTF) and FLASH accelerator are reported

RF Heat Load Compensation with Electrical Heaters for XFEL Accelerator–Measurements at CMTB, AMTF and FLASH

Since 2007, the European X-ray Free Electron Laser (XFEL) is being constructed at DESY, Germany. 800 superconducting niobium 1.3 GHz nine cell cavities and 100 superconducting magnet packages will be operated in a liquid helium II bath at 2K. The static and dynamic heat loads at 2K result in a vapour mass flow up to 96 g/s at 3100 Pa. A four stage cold compressor system is used to return the vapour to the XFEL helium refrigerator. Relative pressure oscillations of the helium II bath should be kept below 1% for stable RF operation of the cavities. In addition, fast changes of vapour pressure and mass flow at the inlet of the cold compressors must be avoided during variation of RF load, e.g. due to switching on/off of RF power or due to cavity quenches. Electrical heaters in the helium II bath of the XFEL linac will be used to compensate the RF load changes. The concept and results of measurements performed at Cryo Module Test Bench (CMTB), Accelerator Module Test Facility (AMTF) and FLASH accelerator are reported