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P. Raimondi

Publications and source records attributed to P. Raimondi.

At least 37 records · Page 2Linked to original sources
arXiv2006

Wire Compensation of Parasitic Crossings in DAFNE

Long-range beam-beam interactions (parasitic crossings) are one of the main luminosity performance limitations for the Frascati e+e- Phi-factory DAFNE. In particular, the parasitic crossings lead to a substantial lifetime reduction of both beams in collision. This puts a limit on the maximum storable current and, as a consequence, on the achievable peak and integrated luminosity. In order to alleviate the problem numerical and experimental studies of the parasitic crossings compensation with current-carrying wires have been performed at DAFNE. Two such wires have been installed at both ends of the KLOE interaction region. Switching on the wires in agreement with the numerical predictions, improvement in the lifetime of the 'weak' beam (positrons) has been obtained at the maximum current of the 'strong' one (electrons) without luminosity loss. In this paper we describe the parasitic crossings effects in DAFNE, summarize the results of numerical simulations on their compensation with the wires and discuss the experimental measurements and observations.

physics.acc-ph↗
arXiv2006

DAFNE Experience with Negative Momentum Compaction

There are several potential advantages for a collider operation with a lattice with negative momentum compaction factor (alfa). Since the lattice of the Frascati e+e- Phi-factory DAFNE is flexible enough to provide collider operation even with alfa < 0, we have exploited this possibility for an experimental study of the beam dynamics. The negative momentum compaction lattices have been successfully implemented and stable 1 A currents have been stored in both electron and positron rings without any problem for RF cavities and feedback systems operation. First collisions have been tested at low currents. In this paper we describe the experimental results and compare them with expectations and numerical simulations. Present limitations to DAFNE operation with alfa < 0 and ways to overcome them are also discussed.

physics.acc-ph↗
arXiv2006

Parameters for a Super-Flavor-Factory

A Super Flavor Factory, an asymmetric energy e+e- collider with a luminosity of order 10^36 cm-2s-1, can provide a sensitive probe of new physics in the flavor sector of the Standard Model. The success of the PEP-II and KEKB asymmetric colliders in producing unprecedented luminosity above 10^34 cm-2s-1 has taught us about the accelerator physics of asymmetric e+e- colliders in a new parameter regime. Furthermore, the success of the SLAC Linear Collider and the subsequent work on the International Linear Collider allow a new Super-Flavor collider to also incorporate linear collider techniques. This note describes the parameters of an asymmetric Flavor-Factory collider at a luminosity of order 10^36 cm-2s-1 at the Upsilon(4S) resonance and about 10^35 cm-2s-1 at the Tau production threshold. Such a collider would produce an integrated luminosity of about 10,000 fb-1 (10 ab-1) in a running year (10^7 sec) at the Upsilon(4S) resonance.

physics.acc-ph↗
arXiv2005

SuperB: a linear high-luminosity B Factory

This paper is based on the outcome of the activity that has taken place during the recent workshop on "SuperB in Italy" held in Frascati on November 11-12, 2005. The workshop was opened by a theoretical introduction of Marco Ciuchini and was structured in two working groups. One focused on the machine and the other on the detector and experimental issues. The present status on CP is mainly based on the results achieved by BaBar and Belle. Estabilishment of the indirect CP violation in B sector in 2001 and of the direct CP violation in 2004 thanks to the success of PEP-II and KEKB e+e- asymmetric B Factories operating at the center of mass energy corresponding to the mass of the Y(4s). With the two B Factories taking data, the Unitarity Triangle is now beginning to be overconstrained by improving the measurements of the sides and now also of the angles alpha, and gamma. We are also in presence of the very intriguing results about the measurements of sin(2 beta) in the time dependent analysis of decay channels via penguin loops, where b --> s sbar s and b --> s dbar d. Tau physics, in particular LFV search, as well as charm and ISR physics are important parts of the scientific program of a SuperB Factory. The physics case together with possible scenarios for the high luminosity SuperB Factory based on the concepts of the Linear Collider and the related experimental issues are discussed.

physics.ins-det↗
arXiv2005

Design of a Polarised Positron Source Based on Laser Compton Scattering

We describe a scheme for producing polarised positrons at the ILC from polarised X-rays created by Compton scattering of a few-GeV electron beam off a CO2 or YAG laser. This scheme is very energy effective using high finesse laser cavities in conjunction with an electron storage ring.

physics.acc-ph↗
arXiv2004

Design considerations for future DAFNE upgrade

The Frascati F-Factory DAFNE has been delivering luminosity to the KLOE, DEAR and FINUDA experiments since year 2000. Since April 2004 the KLOE run has been resumed and recently peak luminosity of 1.0x1032 cm-2s-1 and integrated luminosity of 6.2 pb-1/day have been achieved. The scientific program of the three high-energy experiments sharing DAFNE operation will be completed approximately by the end of year 2006. A scientific program for DAFNE beyond that date has not been defined yet and it is matter of discussion in the high-energy physics and accelerator physics communities. In this paper we present some future scenarios for DAFNE, discussing the expected ultimate performances of the machine as it is now and addressing the design for an energy and/or luminosity upgrade. The options presented in the following are not exhaustive and they are intended to give a glance of what is doable using the existing infrastructures.

physics.acc-ph↗
arXiv2004

DAFNE operation with the FINUDA experiment

DAFNE operation restarted in September 2003, after a six month shut-down for the installation of FINUDA, a magnetic detector dedicated to the study of hypernuclear physics. FINUDA is the third experiment running on DAFNE and operates while keeping on place the other detector KLOE. During the shut-down both Interaction Regions have been equipped with remotely controlled quadrupoles in order to operate at different solenoid fields. Among many other hardware upgrades one of the most significant is the reshaping of the wiggler pole profile to improve the field quality and the machine dynamic aperture. Commissioning of the collider in the new configuration has been completed in short time. The peak luminosity delivered to FINUDA has reached 6 10^31 s-1cm-2, with a daily integrated value close to 4 pb-1.

physics.acc-ph↗
arXiv2004

DAFNE

The results of 2002 DAFNE operation for the two experiments KLOE and DEAR are described. During 2003 a long shutdown has been dedicated to the installation of new Interaction Regions (IR) and to hardware modifications and upgrades. In the last section optics studies and performances expectations for the new machine configuration are reported.

physics.acc-ph↗
arXiv2004

Strong RF focusing for luminosity increase: short bunches at the IP

One of the key-issues to increase the luminosity in the next generation particle factories is to reduce the bunch length at the interaction point (IP) as much as possible. This will allow reducing proportionally the transverse beta functions at the IP and increasing the luminosity by the same factor. The strong RF focusing consists in obtaining short bunches by substantially increasing the lattice momentum compaction and the RF gradient. In this regime the bunch length is modulated along the ring and could be minimized at the IP. If the principal impedance generating elements of the ring are located where the bunch is long (in the RF cavities region) it is possible to avoid microwave instability and excessive bunch lengthening due to the potential well distortion.

physics.acc-ph↗
arXiv2003

Strong RF Focusing for Luminosity Increase

A luminosity of a circular collider can be increased by squeezing the bunch length at the interaction point (IP). A natural way to decrease the bunch length is to decrease the momentum compaction factor and/or to increase the RF voltage. However, in such a way we cannot obtain short bunches with high currents since wakefields prevent this due to the potential well distortion and the microwave instability. In present paper we propose to use a strong RF focusing (with high RF voltage and high momentum compaction factor) to obtain very short bunches at the IP with progressive bunch elongation towards the RF cavity. This allows placing the most important impedance generating elements near the RF cavity where the bunch is longest thus minimizing the effect of the wakefields.

physics.acc-ph↗
arXiv2002

Tuning Knobs for the NLC Final Focus

Compensation of optics errors at the Interaction Point (IP) is essential for maintaining maximum luminosity at the NLC. Several correction systems (knobs) using the Final Focus sextupoles have been designed to provide orthogonal compensation of linear and the second order optics aberrations at IP. Tuning effects of these knobs on the 250 GeV beam were verified using tracking simulations.

physics.acc-ph↗
arXiv2002

NLC Luminosity as a Function of Beam Parameters

Realistic calculation of NLC luminosity has been performed using particle tracking in DIMAD and beam-beam simulations in GUINEA-PIG code for various values of beam emittance, energy and beta functions at the Interaction Point (IP). Results of the simulations are compared with analytic luminosity calculations. The optimum range of IP beta functions for high luminosity was identified.

physics.acc-ph↗
arXiv2001

Observation of Plasma Focusing of a 28.5 GeV Positron Beam

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order Tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0 +/- 0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations.

physics.acc-ph↗
arXiv2001

Feedback Systems for Linear Colliders

Feedback systems are essential for stable operation of a linear collider, providing a cost-effective method for relaxing tight tolerances. In the Stanford Linear Collider (SLC), feedback controls beam parameters such as trajectory, energy, and intensity throughout the accelerator. A novel dithering optimization system which adjusts final focus parameters to maximize luminosity contributed to achieving record performance in the 1997-98 run. Performance limitations of the steering feedback have been investigated, and improvements have been made. For the Next Linear Collider (NLC), extensive feedback systems are planned as an intregal part of the design. Feedback requiremetns for JLC (the Japanese Linear Collider) are essentially identical to NLC; some of the TESLA requirements are similar but there are significant differences. For NLC, algorithms which incorporate improvements upon the SLC implementation are being prototyped. Specialized systems for the damping rings, rf and interaction point will operate at high bandwidth and fast response. To correct for the motion of individual bunches within a train, both feedforward and feedback systems are planned. SLC experience has shown that feedback systems are an invaluable operational tool for decoupling systems, allowing precision tuning, and providing pulse-to-pulse diagnostics. Feedback systems for the NLC will incorporate the key SLC features and the benefits of advancing technologies.

physics.acc-ph↗
arXiv2000

Beam-based Feedback Simulations for the NLC Linac

Extensive beam-based feedback systems are planned as an integral part of the Next Linear Collider (NLC) control system. Wakefield effects are a significant influence on the feedback design, imposing both architectural and algorithmic constraints. Studies are in progress to assure the optimal selection of devices and to refine and confirm the algorithms for the system design. We show the results of initial simulations, along with evaluations of system response for various conditions of ground motion and other operational disturbances.

physics.acc-ph↗
arXiv2000

Simulation Studies of the NLC with Improved Ground Motion Models

The performance of various systems of the Next Linear Collider (NLC) have been studied in terms of ground motion using recently developed models. In particular, the performance of the beam delivery system is discussed. Plans to evaluate the operation of the main linac beam-based alignment and feedback systems are also outlined.

physics.acc-ph↗
arXiv2000

Results on Plasma Focusing of High Energy Density Electron and Positron Beams

We present results from the SLAC E-150 experiment on plasma focusing of high energy density electron and, for the first time, positron beams. We also discuss measurements on plasma lens-induced synchrotron radiation, longitudinal dynamics of plasma focusing, and laser- and beam-plasma interactions.

physics.acc-ph↗