A dynamic momentum compaction factor lattice for improvements to stochastic cooling in storage rings

• Main Author: Olivieri, David Nicholas
• Language: ENG
• Published: ScholarWorks@UMass Amherst 1996
• Subjects: Particle physics|Electromagnetism|Fluid dynamics|Gases
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9639013

A dynamic momentum compaction factor, also referred to as a dynamic $\Delta\gamma\sb{t}$, lattice for the FNAL Antiproton Source Debuncher Storage Ring is studied, both theoretically and experimentally, for the purpose of improving stochastic precooling, and hence, improving the global antiproton production and stacking performance. A dynamic $\Delta\gamma\sb{t}$ lattice is proposed due to the competing requirements inherent within the Debuncher storage ring upon $\gamma\sb{t}$. Specifically, the Debuncher storage ring performs two disparate functions, (i) accepting and debunching a large number of ps/pulse at the outset of the production cycle, which would perform ideally with a large value of $\gamma\sb{t}$, and (ii) subsequently employing stochastic cooling throughout the remainder of the p production cycle for improved transfer and stacking efficiency into the Accumulator, for which a small value $\gamma\sb{t}$ is ideal in order to reduce the diffusive heating caused by the mixing factor. In the initial design of the Debuncher optical lattice, an intermediate value of $\gamma\sb{t}$ was chosen as a compromise between the two functional requirements. The goal of the thesis is to improve stochastic precooling by changing $\gamma\sb{t}$ between two desired values during each p production cycle. In particular, the dynamic $\Delta\gamma\sb{t}$ lattice accomplishes a reduction in $\gamma\sb{t}$, and hence the mixing factor, through an uniform increase to the dispersion throughout the arc sections of the storage ring. Experimental measurements of cooling rates and system performance parameters, with the implementation of the dynamic $\Delta\gamma\sb{t}$ lattice, are in agreement with theoretical predictions based upon a detailed integration of the stochastic cooling Fokker Planck equations. Based upon the consistency between theory and experiment, predictions of cooling rates are presented for future operational parameters of the Antiproton Source with the dynamic $\Delta\gamma\sb{t}$.