4. Conclusions

The betatron tune measurement system has been successfully tested during 51th run of the Nuclotron. The implementation of a high resolution FFT algorithm in an FPGA has allowed the acquisition of continuous real-time betatron tune. The implementation of a digital frequency synthesizer (DFS) inside the FPGA module allowed one to produce chirp and white noise excitation signals. The further improvements are planned to increase the resolution and sensitivity of the measurement system:

• The development of the additional digitizer module with two AD7960, 18-Bit, 5 MSPS PulSAR differential ADC and ACAM TDC-GP22 time measurement controller for precision beam revolution frequency measurement with 90ps resolution. It will allow one to use diode detection technique which can improve the tune measurement resolution by one order of the magnitude [8]. The new digitizer module especially designed to be sampled at the revolution frequency. Simultaneous measurement using two FlexRIO digitizer modules can be a test for the measurement system – Q values should be the same.

• The development of the differential amplifier for pickup based on AD8338, which is a variable gain amplifier (VGA) for applications that require a fully differential signal path, low power, low noise, and a well-defined gain over frequency. It has the voltage controlled gain range of 0dB to 80dB. This amplifier can significantly improve SNR and provide continuous signal fitting into the dynamic range of the ADC, which will allow one to track the betatron tune during injection and acceleration.

5. References

[1] F. Zimmermann, Measurement and Correction of Accelerator Optics. Stanford Linear Accelerator Center (SLAC), Stanford University, Stanford, CA 94309, USA, SLAC-PUB-7844, June 1998.

[2] G.Trubnikov, I.Meshkov, A.Butenko et al. NICA collider complex: challenges and perspectives. Status of the Project. JINR-SAR Round Table, 05 July 2015.

[3] A. Boccardi, M. Gasior, R. Jones et al. The FPGA-based continious FFT tune measurement system for the LHC and its test at the CERN SPS. European Organization for Nuclear Research, CERN – AB Department, CERN-AB-2007-062, Geneva, Switzerland, August 2007.

[4] M. Gasior, J.L. Gonzalez, Improving FFT frequency measurement resolution by parabolic and gaussian interpolation. European Organization for Nuclear Research, CERN – AB division, AB-Note-2004-021 BDI, Geneva, Switzerland, February 2004.

[5] http://www.ni.com/labview/fpga

[6] http://www.tegam.com/product.asp?modelNumber=4040A&redirected=1

[7] http://www.tango-controls.org

[8] M. Gasior and R. Jones. High Sensitivity Tune Measurement by Direct Diode Detection. DIPAC05, Lyon, France, 2005.