Electron Lens as Beam-Beam Wire Compensator in HL-LHC

Current wires are considered for compensation of long-range beam-beam interactions for the High Luminosity upgrade (HL-LHC) of the Large Hadron Collider at CERN. In this note, we demonstrate the advantage of using Electron Lens for this purpose instead of a conventional current-bearing wire

Detection of coherent beam-beam modes with digitized beam position monitor signals

A system for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations in the Fermilab Tevatron collider is described. It is based on the signal from a single beam-position monitor located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, band-limited noise is applied to the beam for about 1 s. This excitation does not adversely affect the circulating beams even at high luminosities. The device has a response time of a few seconds, a frequency resolution of $1.6\times 10^{-5}$ in fractional tune, and it is sensitive to oscillation amplitudes of 60 nm. It complements Schottky detectors as a diagnostic tool for tunes, tune spreads, and beam-beam effects. Measurements of coherent mode spectra are presented and compared with models of beam-beam oscillations.Comment: 7 pages, 4 figures. Submitted to the Proceedings of the ICFA Mini-Workshop on Beam-beam Effects in Hadron Colliders (BB2013), Geneva, Switzerland, 18-22 March 201

Experimental study of vapor-cell magneto-optical traps for efficient trapping of radioactive atoms

We have studied magneto-optical traps (MOTs) for efficient on-line trapping of radioactive atoms. After discussing a model of the trapping process in a vapor cell and its efficiency, we present the results of detailed experimental studies on Rb MOTs. Three spherical cells of different sizes were used. These cells can be easily replaced, while keeping the rest of the apparatus unchanged: atomic sources, vacuum conditions, magnetic field gradients, sizes and power of the laser beams, detection system. By direct comparison, we find that the trapping efficiency only weakly depends on the MOT cell size. It is also found that the trapping efficiency of the MOT with the smallest cell, whose diameter is equal to the diameter of the trapping beams, is about 40% smaller than the efficiency of larger cells. Furthermore, we also demonstrate the importance of two factors: a long coated tube at the entrance of the MOT cell, used instead of a diaphragm; and the passivation with an alkali vapor of the coating on the cell walls, in order to minimize the losses of trappable atoms. These results guided us in the construction of an efficient large-diameter cell, which has been successfully employed for on-line trapping of Fr isotopes at INFN's national laboratories in Legnaro, Italy.Comment: 9 pages, 7 figures, submitted to Eur. Phys. J.

Ambient betatron motion and its excitation by ghost lines in Tevatron

Transverse betatron motion of the Tevatron proton beam is measured and analyzed. It is shown that the motion is coherent and excited by external sources of unknown origins. Observations of the time varying ghost lines in the betatron spectra are reported.Comment: 9 p

Collimation with hollow electron beams

A novel concept of controlled halo removal for intense high-energy beams in storage rings and colliders is presented. It is based on the interaction of the circulating beam with a 5-keV, magnetically confined, pulsed hollow electron beam in a 2-m-long section of the ring. The electrons enclose the circulating beam, kicking halo particles transversely and leaving the beam core unperturbed. By acting as a tunable diffusion enhancer and not as a hard aperture limitation, the hollow electron beam collimator extends conventional collimation systems beyond the intensity limits imposed by tolerable losses. The concept was tested experimentally at the Fermilab Tevatron proton-antiproton collider. The first results on the collimation of 980-GeV antiprotons are presented.Comment: 4 pages, 5 figure

Development of hollow electron beams for proton and ion collimation

Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.Comment: 3 pp. 1st International Particle Accelerator Conference: IPAC'10, 23-28 May 2010: Kyoto, Japa

EVALUATION OF ELECTROMYOGRAPHIC ACTIVITY OF THYROHYOIDEUS (TH) MUSCLE AND ULTRASONOGRAPHIC ASSESSMENT OF THE POSITION OF THE HYOID APPARATUS AT REST AND THEIR POSSIBLE ROLE IN THE PATHOGENESIS OF INTERMITTENT DORSAL DISPLACEMENT OF THE SOFT PALATE (DDSP) IN RACEHORSES.

Introduction Dorsal displacement of the soft palate (DDSP) is one of the most common intermittent dysfunctions of the nasopharynx in racehorses. The DDSP etiopathogenesis is, still today, not clearly understood. Recently was induced DDSP in horses during exercise after bilateral resection of thyrohyoideus (TH) muscles. DDSP was also correlated to a more ventral position of the basihyoid bone evaluated using ultrasonographic scan of the laryngohyoid region. Objectives The purpose of the present work is to investigate TH activity at rest in horses affected with DDSP using surface electromyography (EMG) and correlate the results with the position of hyoid apparatus using ultrasonographic scan of the laringohyoid region. Materials and method 12 racehorses (10 Standardbreds and 2 Thoroughbreds), referred with history of poor performance ranged in age between 2 and 4 years (mean age 3.1 \ub1 0,7 years) with a mean body weight of 468,9 \ub1 52,3 kg. All horses underwent a thorough diagnostic protocol, including examination at rest and during exercise of different body systems, ultrasonographic scan of the laryngeal-hyoid portion and EMG evaluation of TH muscles. Exercise tests were realized using an high-speed treadmill (SATO-I, Sweden) and all the exercise tests was performed using a standardized protocol. On day 4 the treadmill endoscopy using a videoendoscope (Stortz\uae-Germany) held in position with Velcro straps was performed. After videoendoscopy of the upper respiratory tract on treadmill horses were classified into one of two groups based: DDSP when the caudal border of the epiglottis was situated dorsal to the epiglottis for a minimum of 8 s and horses without DDSP if DDSP wasn\u2019 t discovered.. Ultrasonographic scan of the laryngohyoid region comprised two acoustic windows the rostroventral and the midventral, scanned in longitudinal and transverse planes. Using the electronic caliper of the machine were measured the depth of the basihyoid bone at the base of lingual process, the depth of the caudal aspect of the basihyoid bone, the depth of the rostral aspect of the thyroid cartilage, and the distance from the caudal aspect of the basihyoid bone to the rostral aspect of the thyroid cartilage. The EMG activity of the TH muscles was evaluated at rest with surface electrodes and a ground obtained with a subcutaneous needle electrode. The was applied on both sides at the level of the topographic area corresponding to the TH muscle, which was clipped and cleaned with alcohol. TH activity was measured during deglutition obtained following administration of 50 ml of water in the mouth using a 50 ml syringe. This operation was repeated at least five time for each side and every activity connected with deglutition recorded. Electromyographic signals were processed and analyzed and the mean electrical activity (MEA) of the muscles was evaluated. The statistical analysis of the results was made comparing the two groups, horses with DDSP (wDDSP) and without DDSP (nDDSP), considering all the measures of the laryngohyoid position, the MEA of TH muscle on the left side (MEAl), the MEA of TH muscle on the right side (MEAr) and mean MEA obtained from the two sides (MEArl) for every horse. The analysis was realized with a statistical software SIGMAPlot\uae12. Using SIGMAPlot\uae12 was realized a Shapiro-Wilk test to assess the normal distribution of the data followed by a t-test to compare every data between the group wDDSP and nDDSP. Next a Pearson Product Moment Correlation was used to evaluate the correlation between the different data in nDDSP and wDDSP groups. Finally the relationship between age, sex and weight on MEAr, MEAl, MEArl and laringohyoid measures was analyzed using a linear regression test. For all statistical analysis, values were considered significant at P 64 0.05. Results The videoendoscopy of the upper airways during exercise on a high speed treadmill permitted to diagnose DDSP in 5 horses (4 standardbred and 1 Throughbred), pharyngeal collapse in 1 horse, pharyngeal collapse associated with axial deviation of the aryepiglottic folds (ADAF) in 2 horses and no dynamic abnormality of the upper respiratory tract (URT) in 4 horses. The statistical analysys, using Pearson Product Moment Correlation test, showed only in the wDDSP group some correlation between the data analyzed. A strong correlation (p. 0,0019) was found between the depth of the basihyoid bone at the base of lingual process and depth of the rostral aspect of the thyroid cartilage on the midventral window. Another strong correlation (p. 0,0092) was found between depth of the rostral aspect of the thyroid cartilage and depth of the caudal aspect of the basihyoid bone in the midventral window. Finally, strong correlations were found between MEAr and MEAl (p. 0,0039), MEAr and MEArl (p. 0,0005) and MEAl and MEArl (p. 0,0004). No other difference or correlation were found. Discussion and conclusion: Our results didn\u2019t identify any statistical difference in laringohyoid measures between nDDSP and wDDSP groups. Anyway, in wDDSP group we found a high correlation between some ultrasonographic measures obtained confirming the importance of the connection between hyoid apparatus and larynx in DDSP patients. We didn\u2019t find any difference between MEA in nDDSP and wDDSP patients at rest. Probably, our results are directly conditioned by the type of test realized. Probably more information regarding the activity of TH muscles could be obtained with the evaluation during exercise. The results obtained provide informations regarding the pathogenesis of intermittent DDSP. Future results obtained with the evaluation of the same parameters under exercise conditions may aid the clinician to identify the actual causes for DDSP