Recycler barrier RF buckets

The Recycler Ring at Fermilab uses a barrier rf system for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf systems, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.Comment: 30 pp. Submitted as a chapter in a book on the Tevatron edited by Valeri Lebedev and Vladimir Shiltse

Longitudinal Momentum Mining of Beam Particles in a Storage Ring

I describe a new scheme for selectively isolating high density low longitudinal emittance beam particles in a storage ring from the rest of the beam without emittance dilution. I discuss the general principle of the method, called longitudinal momentum mining, beam dynamics simulations and results of beam experiments. Multi-particle beam dynamics simulations applied to the Fermilab 8 GeV Recycler (a storage ring) convincingly validate the concepts and feasibility of the method, which I have demonstrated with beam experiments in the Recycler. The method presented here is the first of its kind.Comment: 11 pages, 3 figure

The Fermilab Main Injector: current status and future

The Fermilab Main Injector is a 8-150 GeV proton synchrotron being built as a high intensity injector to the Tevatron. The design incorporates many novel features to achieve {ital p{anti p}} luminosity in the Tevatron exceeding 8 x 10{sup 31} cm{sup -2}sec{sup -1}. An overview of the Main Injector project, current status and future prospects will be discussed

A new method for beam stacking in storage rings

Recently, I developed a new beam stacking scheme for synchrotron storage rings called 'longitudinal phase-space coating' (LPSC). This scheme has been convincingly validated by multi-particle beam dynamics simulations and has been demonstrated with beam experiments at the Fermilab Recycler. Here, I present the results from both simulations and experiments. The beam stacking scheme presented here is the first of its kind

Applications of barrier bucket RF systems at Fermilab

In recent years, the barrier rf systems have become important tools in a variety of beam manipulation applications at synchrotrons. Four out of six proton synchrotrons at Fermilab are equipped with broad-band barrier rf systems. All of the beam manipulations pertaining to the longitudinal phase space in the Fermilab Recycler (synchrotron used for antiproton storage) are carried out using a barrier system. Recently, a number of new applications of barrier rf systems have been developed- the longitudinal momentum mining, longitudinal phase-space coating, antiproton stacking, fast bunch compression and more. Some of these techniques have been critical for the recent spectacular success of the collider performance at the Fermilab Tevatron. Barrier bunch coalescing to produce bright proton bunches has a high potential to increase proton antiproton luminosity significantly. In this paper, I will describe some of these techniques in detail. Finally, I make a few general remarks on issues related to barrier systems

Some design considerations for pbar target sweeping station

This report summarizes the results of some recent calculations useful to design the beam sweeping station to produce high intensity pbar beam at AP0. With various on-going and planned intensity upgrade at the accelerator including the main injector the primary beam intensity on the pbar target is expected to increase. But some complications would arise from the existing method of pbar production. A study of the heavy metal targets used when the beam intensity was about 1.0 {times} 10{sup 12}, has shown a clear indication of target destruction by the proton beam. Although the heavy metal has very high melting point temperature the thermoelastic property is not suitable for its use as a reliable pbar target. During 1989 collider run, the target material was changed over to copper because of its better thermoelastic properties. The pbar yield measurement did not show much indications of target destruction except for a small decrease in the pbar yield. However, the calculations showed that the target material along the beam might have had enough energy deposition to transform the target material from the solid state to the liquid state during the beam spill time. A further increase of the proton beam intensity might cause melting of the target and drill a hole. These problems stimulated this investigation of suitable target materials and a method to handle the high intensity proton beam. Properties of a number of target materials have been studied in terms of their mechanical strength/resistance to shock-waves i.e. their thermoelastic behaviour

Effect of retrogression and re-ageing heat treatment on microstructure and microhardness of aluminium 7010 alloy.

Aluminium alloy 7010 is subjected to retrogression and re-ageing (RRA) heat treatment to study the influence of microstructural changes on hardness. Retrogression is performed at 190 °C for different time intervals ranging from 10 to 60 minutes. Optimum time for retrogression treatment is estimated based on the retrogression time that result with equivalent mechanical properties as that of peak aged (T6) condition. Retrogression performed for 30 minutes resulted with micro hardness of 203 HV, which is equivalent to that obtained by following T6treatment. Microstructural characterization done with the help of transmission electron microscope (TEM) indicates RRA treatment results with the coarsened and discontinuous precipitates along the grain boundary which is similar to over aged (T7) condition, where as fine and densely populated precipitates in the matrix similar to T6 condition. Coarse and discontinuous grain boundary precipitates(GBP’s)improves resistance to stress corrosion cracking. Fine and dense precipitates in the matrix ensureshardness equivalent to that of T6

Engineering of Cyclodextrin Product Specificity and pH Optima of the Thermostable Cyclodextrin Glycosyltransferase from Thermoanaerobacterium thermosulfurigenes EM1

The product specificity and pH optimum of the thermostable cyclodextrin glycosyltransferase (CGTase) from Thermoanaerobacterium thermosulfurigenes EM1 was engineered using a combination of x-ray crystallography and site-directed mutagenesis. Previously, a crystal soaking experiment with the Bacillus circulans strain 251 β-CGTase had revealed a maltononaose inhibitor bound to the enzyme in an extended conformation. An identical experiment with the CGTase from T. thermosulfurigenes EM1 resulted in a 2.6-Å resolution x-ray structure of a complex with a maltohexaose inhibitor, bound in a different conformation. We hypothesize that the new maltohexaose conformation is related to the enhanced α-cyclodextrin production of the CGTase. The detailed structural information subsequently allowed engineering of the cyclodextrin product specificity of the CGTase from T. thermosulfurigenes EM1 by site-directed mutagenesis. Mutation D371R was aimed at hindering the maltohexaose conformation and resulted in enhanced production of larger size cyclodextrins (β- and γ-CD). Mutation D197H was aimed at stabilization of the new maltohexaose conformation and resulted in increased production of α-CD. Glu258 is involved in catalysis in CGTases as well as α-amylases, and is the proton donor in the first step of the cyclization reaction. Amino acids close to Glu258 in the CGTase from T. thermosulfurigenes EM1 were changed. Phe284 was replaced by Lys and Asn327 by Asp. The mutants showed changes in both the high and low pH slopes of the optimum curve for cyclization and hydrolysis when compared with the wild-type enzyme. This suggests that the pH optimum curve of CGTase is determined only by residue Glu258.

Envelope and multi-slit emittance measurements at Fermilab A0 photoinjector and comparison with simulations

Recently we have measured the envelope and the transverse emittance of an 0.85 nC electron beam at the Fermilab A0-Photoinjector facility. The transverse emittance measurement was performed using the multi-slit method. The data have been taken with an unstacked 2.8 ps laser pulse. In this paper we report on these beam measurements and compare the results with the predictions from beam dynamics codes ASTRA and GPT using 3D space charge routines