No Arabic abstract
A new 4-rod RFQ was commissioned at the UNILAC in 2009, it went into operation in 2010. At high rf amplitudes strong modulations of the rf reflection emerge. They are attributed to mechanical oscillations of the rods, excited by the rf pulse. As these modulations could so far only be seen during the rf pulse by means of rf measurements, a direct observation of the mechanical vibrations was desirable. Such measurements have been conducted using a commercial laser vibrometer, allowing the investigation of the mechanical behavior of the RFQ in situ and independent of the presence of rf power. Results from investigations under standard operation conditions confirm the vibrations as the source of the modulations observed by rf as well as their excitation by the rf pulse. Further measurements revealed more details about the excitation process, leading to a better understanding and possibly new ways of mitigation.
This paper presents measurements of the beam transmission performed on the 4-rod RFQ currently under operation at Fermilab. The beam current has been measured at the RFQ exit as a function of the magnetic field strength in the two LEBT solenoids. This measurement is compared with scans performed on the FermiGrid with the beam dynamics code TRACK. A particular attention is given to the impact, on the RFQ beam transmission, of the space-charge neutralization in the LEBT.
We present measurements of mechanical vibrations induced by 0.6 GeV electrons impinging on cylindrical and spherical aluminium resonators. To monitor the amplitude of the resonators vibrational modes we used piezoelectric ceramic sensors, calibrated by standard accelerometers. Calculations using the thermo-acoustic conversion model, agree well with the experimental data, as demonstrated by the specific variation of the excitation strengths with the absorbed energy, and with the traversing particles track positions. For the first longitudinal mode of the cylindrical resonator we measured a conversion factor of 7.4 +- 1.4 nm/J, confirming the model value of 10 nm/J. Also, for the spherical resonator, we found the model values for the L=2 and L=1 mode amplitudes to be consistent with our measurement. We thus have confirmed the applicability of the model, and we note that calculations based on the model have shown that next generation resonant mass gravitational wave detectors can only be expected to reach their intended ultra high sensitivity if they will be shielded by an appreciable amount of rock, where a veto detector can reduce the background of remaining impinging cosmic rays effectively.
The RFQ design tool DEMIRCI aims to provide fast and accurate simulation of a light ion accelerating cavity and of the ion beam in it. It is a modern tool with a graphical user interface leading to a point and click method to help the designer. This article summarises the recent software developments such as the addition of RFQ acceptance match, beam dynamics and 8-term potential coefficient calculations. Its results are compared to other similar software, to discuss the attained compatibility level.
The development and production of radio frequency quadrupoles, which are used for accelerating low-energy ions to high energies, continues since 1970s. The development of RFQ design software packages, which can provide ease of use with a graphical interface, can visualize the behavior of the ion beam inside the RFQ, and can run on both Unix and Windows platforms, has become inevitable due to increasing interest around the world. In this context, a new RFQ design software package, DEMIRCI, has been under development. To meet the user expectations, a number of new features have been recently added to DEMIRCI. Apart from being usable via both graphical interface and command line, DEMIRCI has been enriched with beam dynamics calculations. This new module gives users the possibility to define and track an input beam and to monitor its behavior along the RFQ. Additionally, the Windows OS has been added to the list of supported platforms. Finally, the addition of more realistic 8 term potential results has been ongoing. This note will summarize the latest developments and results from DEMIRCI RFQ design software.
We consider two dielectric membranes suspended inside a Fabry-Perot-cavity, which are cooled to a steady state via a drive by suitable classical lasers. We show that the vibrations of the membranes can be entangled in this steady state. They thus form two mechanical, macroscopic degrees of freedom that share steady state entanglement.