9667751
Quasi-Optimal Algorithms for the Control Loops of the Fermilab Energy Saver Satellite Refrigerator
The Cryogenic System of the Satellite Refrigerator for the Energy Saver Accelerator Ring comprises 12 interrelated closed loops and several open loops. A quasi-optimal algorithm to control the Cryogenic System, under different modes operation, is described. The constraints imposed to define these algorithms and the process followed to characterize the functional parameters are described. A report on the results obtained with the algorithms in a test facility will be presented.
45030934
Superconducting Delay Line for Stochastic Cooling Filters
The stochastic cooling system of the antiproton source at Fermilab uses notch filters for reducing the feedback power at frequencies corresponding to particles in the core. At the same time these filters assist in shaping the gain vs. momentum in the stack tail. These filters, therefore, must attenuate all the harmonics of the revolution frequency (629 kHz) in the operating frequency band (1-2 GHz). They require components providing delays of 1.59 microseconds with a minimum of attenuation and undesirable distortion in this passband. Transmission lines providing such delays are typically 328 m long, have a rather large diameter, and are fabricated from a high conductivity material to keep the attenuation sufficiently low. The use of superconductors allows a dramatic reduction in the diameter, total size, and cost of this component in spite of the added cryogenic requirements. The authors measured the performance of two such cables in order to demonstrate the feasibility of the superconducting cable-notch filter concept. The first cable is an 84 m long superconducting coax consisting of a solid Niobium inner conductor inside a teflon dielectric, a lead outer conductor, and an outer jacket of mylar tape. The second cable is a 1.0 km long coaxial line more » with an inner conductor of lead-plated copper wire, a FEP teflon dielectric, and an outer conductor of leadplated copper tape wrapped with mylar. This paper discusses the results of performance testing of both cables and assesses their compatibilities with notch filters. « less
55383487
Operational Experience with Tevatron I Antiproton Source
The secondaries are transported down the AP2 line into the Debuncher ring. The Debdncher ring has a 207 x 23~ transverse acceptance and 4% momentum acceptance. The antiprotons are then rotated using 4.2 MV of 53 MHz R.F. to .4% Ap/p in 80 turns and the adIabatically debunched to .2% APIP. The antiproton are then stochastically cooled for 2 seconds in the transverse planes with 2-4 GHz cooling systems to 771 x 77. The antiproton are then extracted from the Debuncher and transported across the D/A line to the Accumulator.
46560389
Helium Refrigeration System and Cryogenic System for Superconducting Switchyard Magnets at Fermilab
The first Fermilab Satellite Refrigerator produced from commercially built components has been operated in the Switchyard in a stand alone mode. After some initial shakedown runs, it has been used to cool two magnetically opposed superconducting magnets in the external beam line to the Meson Laboratory. This equipment was installed as a test of the cryogenic system to be used in converting the entire major horizontal bend to superconducting magnets (currently containing 56 conventional 10 foot dipoles). We report here on the successful operation of the refrigerator, our operating experience with the cryo nic system, and the successful transport of 1.8 x 10'1 350 GeV protons per pulse through the magnets. The complete system was designed and built by Fermilab personnel. Process and component specification and design were shared by Fermilab and an independent consulting firm.1
117708238
STACKTAIL MOMENTUM COOLING IN THE FERMILAB ANTIPROTON SOURCE
121309706
Measurements of magnet quench levels induced by proton beam spray
A superconducting dipole magnet was installed in the Fermilab primary beam line. Targets were inserted in the proton beam upstream of the magnet and measurements made of the energy deposition within the magnet sufficient to cause quenching. The quench levels were 25 mW/g for 1 sec beam spill and 1 mJ/g for a spill of 1 msec or less. In comparison, the energy deposition at the extraction septum was 0.6 mJ/g.
54960779
Measurement of the resonant and CP components in $\overline{B}^0\to J/\psi \pi^+\pi^-$ decays
The resonant structure of the reaction $\overline{B}^0\rightarrow J/\psi \pi^+\pi^-$ is studied using data from 3 fb$^{-1}$ of integrated luminosity collected by the LHCb experiment, one-third at 7 Tev center-of-mass energy and the remainder at 8 Tev. The invariant mass of the $\pi^+\pi^-$ pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. Six interfering $\pi^+\pi^-$ states: $\rho(770)$, $f_0(500)$, $f_2(1270)$, $\rho(1450)$, $\omega(782)$ and $\rho(1700)$ are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative CP fractions of each of the resonant final states are determined. The $f_0(980)$ meson is not seen and the upper limit on its presence, compared with the observed $f_0(500)$ rate, is inconsistent with a model of tetraquark substructure for these scalar mesons at the eight standard deviation level. In the $q\overline{q}$ model, the absolute value of the mixing angle between the $f_0(980)$ and the $f_0(500)$ scalar mesons is limited to be less than $17^{\circ}$ at 90% confidence level.
118667423
Chiral ring in the 4-D W(3) string
I summarize some recent results obtained in collaboration with P.~Bouwknegt and K.~Pilch on the spectrum of physical states in $\cW_3$ gravity coupled to $c=2$ matter. In particular, it is shown that the algebra of operators corresponding to physical states -- defined as a semi-infinite (or BRST) cohomology of the $\cW_3$ algebra -- carries the structure of a G-algebra. This G-algebra has a quotient which is isomorphic to the G-algebra of polyvector fields on the base affine space of $SL(3,\CC)$. Details have appeared elsewhere. To appear (with title change) in the proceedings of the ``H.S. Green and A. Hurst Festschrift: Confronting the Infinite'' Adelaide, March 1994.
3553275
Observation of charmonium pairs produced exclusively in $pp$ collisions
A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of $3{\rm\ fb}^{-1}$ collected at centre-of-mass energies of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges $(-3.5,-1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measured to be $$ \begin{array}{rl} \sigma^{J/\psi J/\psi} &= 58\pm10{(\rm stat)} \pm 6{(\rm syst)} {\rm\ pb} , \\ \sigma^{J/\psi\psi(2S)} &= 63 ^{+27}_{-18}{(\rm stat)}\pm 10{(\rm syst)} {\rm\ pb} , \\ \sigma^{\psi(2S)\psi(2S)} &< 237 {\rm\ pb}, \\ \sigma^{\chi_{c0}\chi_{c0}} &< 69 {\rm\ nb}, \\ \sigma^{\chi_{c1}\chi_{c1}} &< 45 {\rm\ pb}, \\ \sigma^{\chi_{c2}\chi_{c2}} &< 141 {\rm\ pb}, \\ \end{array} $$ where the upper limits are set at the 90% confidence level. The measured $J/\psi J/\psi$ and $J/\psi\psi(2S)$ cross-sections are consistent with theoretical expectations.
45908480
Multi-GeV Electron Linac-Pulse Stretcher Design Options
The Linac-Pulse Stretcher Ring system is evaluated as a design for a high duty factor (> 90%), intense (240 ¿A), electron accelerator for operation in the 0.5 to multi-GeV (> 4 GeV) region. Options within this system are discussed in light of their predicted initial and operational cost, flexibility, and reliability. The ramifications of the choice of a particular cavity type, accelerating gradient, repetition rate, beam pulse length, and number of beam recirculations for the linac design are discussed both with respect to the linac itself and to the Pulse Stretcher Ring. The Pulse Stretcher Ring concept is analysed in terms of injection schemes (single or multi-turn), extraction methods (half or third integer, chromatic or achromatic), and operation parameters (machine tune and chromaticity).
6449730
Design of an electron beam spectral modification system
We report the design of a spectral modification system (SMS) for use with the proposed NEAL linac-pulse stretcher ring, cw electron beam facility. The SMS allows tailoring of the energy distribution of electrons in beams produced by a pulsed linac operating in the transient beam loading (TBL) regime. Modification of the energy distribution of electrons injected into the pulse strecher ring will increase the duty factor of current extracted from the ring and improve the efficiency of the extraction process. Physically, the SMS consists of an anisochronous, achromatic magnetic lattice followed by a pair of traveling-wave accelerating sections. For beams in the energy range of 500 MeV to 4 GeV, TBL ripple on the energy envelope of microsecond long beam spills is expected to be reduced from 1% peak-peak to less than 0.01% while the desired width of the energy profile due to the phase extent of the microbunches in the beam spill is preserved.