Final Focus Quadrupoles Research Articles

Symmetric achromatic low-beta collider interaction region design concept

We present a new symmetry-based concept for an achromatic low-beta collider interaction region design. A specially designed symmetric chromaticity compensation block (CCB) induces an angle spread in the passing beam such that it cancels the chromatic kick of the final focusing quadrupoles. Two such CCBs placed symmetrically around an interaction point allow simultaneous compensation of the 1st-order chromaticities and chromatic beam smear at the IP without inducing significant 2nd-order aberrations to the particle trajectory. We first develop an analytic description of this approach and explicitly formulate 2nd-order aberration compensation conditions at the interaction point. The concept is next applied to develop an interaction region design for the ion collider ring of an electron-ion collider. We numerically evaluate performance of the design in terms of momentum acceptance and dynamic aperture. The advantages of the new concept are illustrated by comparing it to the conventional distributed-sextupole chromaticity compensation scheme.

Design and Manufacture of a Hybrid Final Focus Quadrupole Model for CLIC

A tunable hybrid quadrupole magnet design has been proposed for the final focus in the Compact Linear Collider (CLIC) that is currently under study. The proposed design is a combination of an iron dominated electromagnetic quadrupole with a bore diameter of 8.25 mm with permanent magnet blocks placed between the poles made of soft magnetic CoFe alloy “Permendur”. The possibility of using Sm2Co17 and Nd2Fe14B as material for the permanent magnet blocks has been investigated. It is shown that a very high field gradient of 530 T/m (Sm2Co17)and 590 T/m (Nd2Fe14B)can be achieved.

Development of the Superconducting Quadrupole Magnet for the SuperKEKB Final Focusing System

We have developed the superconducting final-focus quadrupoles for SuperKEKB, the next generation B-factory experiment in Japan. The system consists of four quadrupole doublets for incoming and outgoing electron and positron beams, respectively. A R&D superconducting quadrupole magnet was fabricated. In this paper, we describe the results on the excitation test and the magnetic field measurements of this R&D magnet.

Design and Construction of the Final Focus Quadrupole R&D Magnet for Super-KEKB

For upgrading the electron-positron collider KEKB, the final focusing magnet system in the beam interaction region has been studied. The designed magnet system consists of five superconducting and three permanent quadrupole magnets. A superconducting quadrupole magnet has been constructed as the R&D of this system. In this paper, design and construction of this R&D magnet are reported.

Construction and Testing of the Final Focus Quadrupole R&D Magnet for the Super-KEKB Interaction Region

Super-KEKB is designed to be a next generation particle accelerator with a target luminosity of 4 times 1035 cm-2s-1. For the interaction region, a final focus quadrupole R&D magnet was designed and constructed. The design field gradient and effective magnetic length were 40.12 T/m and 0.299 m, respectively. The magnet consists of 6 layer coils. After construction, the magnet was tested at 4.2 K and a preliminary field measurement was performed. The magnet was energized to a current of 1800 A, which corresponds to 95.8% of the conductor limit, and the quadrupole component error was 0.23 % of the design value.

The stabilisation of final focus system

The StaFF (stabilisation of final focus) system will use interferometers to monitor the relative positions and orientations of several key components in the beamdelivery and interaction region. Monitoring the relative positions of the ILC final focus quadrupole magnets will be the most demanding application, where mutual and beam-relative stability will have a direct impact on machine luminosity. Established, laser-based frequency scanning interferometry (FSI) and fixed-frequency interferometry (FFI) offer positional resolution at length scales of the laser wavelength (1500 nm to 1560 nm) and a thousandth of the wavelength, respectively. As part of the ATF at KEK, StaFF will use interferometers to measure lines of a geodetic network to record relative motion between two beam position monitors. Interferometers are being designed and tested in Oxford prior to deployment at the ATF.

Compensation of detector solenoid effects on the beam size in a linear collider

In this paper, the authors discuss the optics effects of the realistic detector solenoid field on beam size at the Interaction Point (IP) of a future Linear Collider and their compensation. It is shown that most of the adverse effects on the IP beam size arise only from the part of the solenoid field which overlaps and extends beyond the final focusing quadrupoles. It is demonstrated that the most efficient and local compensation can be achieved using weak antisolenoids near the IP, while a correction scheme which employs only skew quadrupoles is less efficient, and compensation with strong antisolenoids is not appropriate. One of the advantages of the proposed antisolenoid scheme is that this compensation works well over a large range of the beam energy

The vacuum system for the upgraded HERA interaction regions

DESY pursues a luminosity upgrade project for the HERA electron–proton collider that foresees an increase of the luminosity by nearly a factor of 5. This is achieved mainly by a completely new layout of the interaction region. The new scheme involves a very early separation of the colliding beams by means of superconducting magnets that are installed inside the experimental detectors. The early beam separation allows the final focus quadrupoles to be located closer to the interaction point (IP), which in turn leads to smaller beam spot-sizes and higher luminosity. The HERA upgrade requires the whole vacuum system in the interaction regions of the machine to be rebuilt. This amounts to about 400 m length of new electron, proton and common vacuum system. The requirements for the vacuum quality were raised in comparison to the present machine, because electrons that lost energy due to beam–gas interactions will be mainly deflected into the detector beam pipes by the superconducting separation magnets. At all possible locations we have foreseen to install NEG pumps. Another critical point is the safe handling of about 30 kW synchrotron radiation power, produced by the separation magnets in the detectors. An overview on the project is presented and some critical issues are discussed with emphasis.

Design of the muon collider lattice: Present status

The last component of a muon collider facility, as presently envisioned, is a colliding-beam storage ring. Design studies on various problems for this ring have been in progress over the past year. In this paper we discuss the current status of the design. The projected muon currents require very low beta values at the IP, {beta}* = 3 mm, in order to achieve the design luminosity of L = 10{sup 35} cm{sup -2} s{sup -1}. The beta values in the final-focus quadrupoles are roughly 400 km. To cancel the corresponding chromaticities, sextupole schemes for local correction have been included in the optics of the experimental insertion. The hour-glass effect constraints the bunch length to be comparable too. To obtain such short bunches with reasonable rf voltage requires a very small value of the momentum compaction a, which can be obtained by using flexible momentum compaction (FMC) modules in the arcs. A preliminary design of a complete collider ring has now been made; it uses an experimental insertion and arc modules as well as a utility insertion. The layout of this ring is shown schematically, and its parameters are summarized. Though some engineering features are unrealistic, and the beam performance needsmore » some improvement, we believe that this study can serve as the basis for a workable collider design. The remaining sections of the paper will describe the lattice, show beam behaviour, and discuss future design studies.« less

The UCLA Phi Factory detector, the integration of superconducting compensation solenoids and the final focus interaction region quadrupoles

The proposed Phi Factory for the University of California at Los Angeles (UCLA) is a small 510 MeV electron-positron colliding beam storage ring with high luminosity (greater than 10 32 cm −2 s −1). In order to do high quality Phi physics, a particle detector system with a large solid angle (preferably greater than 98 percent) is required. Particle detection and analysis will be done within a 0.5 tesla solenoidal magnetic field. The solenoidal field within the detector causes coupling between beam oscillations in the horizontal and vertical directions. Therefore, compensation solenoids are required to keep the circulating particle beams from seeing the effects of the field from the main detector solenoid. Since high luminosity and a large solid angle are required, the detectors and a pair of compensation solenoids must be integrated with the final focus quadrupoles within the detector straight section. This report describes the design of two tapered, 0.5 tesla, superconducting compensation solenoids which must go around six rare earth permanent final focus quadrupoles or six superconducting quadrupoles on either side of the beam collision point. A cryogenic cooling system for these two solenoids, which will be coupled with the cooling system for the primary detector solenoid, is also described.

Construction and test of a model of a pulsed high gradient, final focus quadrupole

Quadrupoles with gradients of well above 10/sup 3/ T/m are required for the focusing of e/sup -//e/sup +/ colliders to achieve the required luminosity. Among other solutions, pulsed single conductor quadrupoles could provide such high gradients. In order to evaluate technical designs, a series of different model quadrupoles with full apertures of 10 mm, about 5-10 times the final required size, was constructed. Electromagnetic tests of these models were carried out in the pulsed regime at the INP, Novosibirsk, where the magnetic fields, gradients, energy consumption, and required voltages were measured. Some of the results are compared to computations achieved with a finite element computer code, taking into account the transient skin effect regime. By scaling the results to final envisaged apertures and gradients, design values are obtained which make it possible to assess further the feasibility of pulsed final focus quadrupoles. >

Computation of design parameters and optimization of a pulsed final focus quadrupole in the transient skin effect regime

Very high gradient quadrupoles are required for the final focusing of e/sup -//e/sup +/ colliders. Quadrupoles, consisting of four single, axial current leads and powered with high-current pulses, represent one of the possible solutions. For the envisaged conductor cross-section and pulse durations, the magnet will operate in the transient skin effect regime. This has been assessed with a finite element computer code. A survey of the effects of the quadrupole geometry and the pulse duration on the magnetic field, the gradient, the energy consumption, the prevailing voltages, and the electromagnetic forces has been made. This makes it possible to identify and quantify the impact of specific parameters on the feasibility, the design, and the limits of such pulsed quadrupoles. >