The 3.9 GHz program marked Fermilabís first effort to build superconducting RF cavities for use at another laboratory. As part of its role in the TESLA collaboration, Fermilab had established a program for producing 3.9 GHz superconducting RF cavities.
Fermilab delivered the assembled cryomodule containing four 3.9 GHz cavities to DESY on 28th April, 2009.
These third harmonic cavities will be used in DESYís TTF/FLASH accelerator, a test facility for superconducting technology and free electron laser.The modules will now be dressed with couplers and then put into the FLASH linear accelerator during a major upgrade this autumn. The 'third harmonic' module is one of Fermilab's contributions to the TESLA Technology Collaboration that built FLASH as a test facility for superconducting radiofrequency technology.