Particle Accelerator Laboratory
Gruppo di Lavoro
The laboratory is devoted to the design and measurement of Radio Frequency (RF) devices for modern particle accelerators. Those devices are designed with the aid of standard software, widely used in modern RF engineering, e.g. Ansoft-HFSS or CST-Microwave Studio; the dynamics of particles inside those devices is also optimised with dedicated tools widely used in the Accelerator Physics community (e.g. TSTEP). The laboratory is equipped with servers dedicated to those softwares.
Vector Networks Analysers (VNA) are used to bench measure any particle accelerator RF device, e.g. acceler-ating and deﬂecting structures, beam position monitors, resonant cavities as well as low power electronics. The laboratory hosts four VNAs operating from few kHz to 20GHz, as well as the necessary mechanical and electronic calibration kits. High frequency signal generators, spectrum analysers and calibrated antennas are also available for Electro-Magnetic compatibility measurements. Typical RF devices, such as ampliﬁers, attenuators, power splitters, directional couplers, ﬁlters, high accuracy cables are also present covering the 20GHz range. All our instruments can be remotely controlled with standard application (such as Labview and Matlab) as well as integrated in complex bench measurements requiring the synchronisation of the instrument with external devices (e.g. step motors).
The laboratory can perform complex, general purpose RF measurements (e.g. Time Domain Reﬂectometry) as well as bench measurements typical of the accelerator engineering, e.g. coaxial wire or bead pull techniques. The Coaxial Wire method is used to estimate the coupling impedance of accelerator devices, a quantity aﬀecting the beam stability in accelerators. Bead pull is used to measure the electro-magnetic ﬁeld acting on the particles both in resonant and non resonant devices; the perturbing object can be calibrated in dedicated pillbox cavities.
Most of the devices designed and measured in the accelerator laboratory are standard S-band (3GHz) devices, in particular deﬂecting cavities; we also measured and tuned C band (6GHz) travelling wave devices before the high power tests. We also designed and measured diﬀerent accelerating multi-cell cavities in X Band (12GHz). All our activity is in tight collaboration with INFN Laboratori Nazionali di Frascati, where such devices are used in operating accelerators.
Figure 1: Bead pull measurement of C band travelling wave device (top left picture), X band standing wave multi-cell cavity (top right picture), students working in the laboratory for the microwave measurement laboratory course (bottom left picture) and S band multi-cell deﬂecting cavity (bottom right picture)