Study of a less invasive LHC early separation scheme

The LHC Early Separation Scheme consists of a four 8 to 15 T-m dipoles (D0s) installed in the two LHC high luminosity experiments. Its aim, in the framework of LHC Phase II Upgrade, is to improve the luminosity by reducing the crossing angle between the two colliding beams, mitigating and controlling at the same time their parasitic interactions. We investigate a less invasive implementation for the detectors (D0 at 14 from the IP) with respect to those already presented (D0 at 4 and 8 m from the IP). The luminosity performance is discussed and a tentative analysis on beam-beam effect impact is given. For the new D0 position, preliminary dipole design and power deposition results are shown

A Feasibility Study of Superconducting Dipole for the Early Separation Scheme of SLHC

In the framework of the LHC luminosity upgrade an early separation scheme is being studied for the final phase ($L\approx 10^{35} cm^{-2} s^{-1}$ with substantial changes in the IR). In this paper we compare a Nb$_{3}$Sn and a Nb-Ti cos($\theta$) design: the aim is to explore the benefits and the limits of a compact solution with respect to the detector's constraints and the energy deposition issues. We propose to put the dipole system (cryostat and magnet) at a location starting at 6.8 m from the IP. The preliminary cross section, the achievable integrated field, the energy deposition on the magnet are presented and discusse

Excitation of longitudinal coupled-bunch oscillations with the wide-band cavity in the CERN PS

Longitudinal coupled-bunch oscillations in the CERN Proton Synchrotron have been studied in the past years and they have been recognized as one of the major challenges to reach the high brightness beam required by the High Luminosity LHC project. In the frame of the LHC Injectors Upgrade project in 2014 a new wide-band Finemet cavity has been installed in the Proton Synchrotron as a part of the coupled-bunch feedback system. To explore the functionality of the Finemet cavity during 2015 a dedicated measurement campaign has been performed. Coupled-bunch oscillations have been excited with the cavity around each harmonic of the revolution frequency with both a uniform and nominal filling pattern. In the following the measurements procedure and results are presented

New Results on the Early Separation Scheme

A new strategy of luminosity leveling using the early separation scheme is proposed. It increases rather than decreases the integrated luminosity to levels above those presently predicted for the LHC luminosity upgrade. The multiplicity is kept under control at about 100

An Early Beam Separation Scheme for the LHC Luminosity Upgrade

The high nominal luminosity of the LHC requires a large number of bunches spaced by about 7.5 m. To prevent more than one head-on collision in each interaction region, a crossing angle of 0.285 mrad is necessary. A side effect of this crossing angle is the increase of the effective transverse beam cross-section, thereby decreasing the luminosity by some 16%. For the LHC luminosity upgrade, depending on the focusing scenarios, this loss significantly increases and largely offsets the potential gain of a stronger focusing. In this paper we analyze a strategy to circumvent this difficulty, based on an early beam separation using small dipoles placed at a few meters from the interaction point. From the beam dynamics point of view, the essential constraint is to control the long-range beamâbeam interactions in a scenario where the normalized beam separation is not constant

A Luminosity Leveling Method for LHC Luminosity Upgrade using an Early Separation Scheme

The very high luminosity foreseen for the LHC luminosity upgrade entails in all cases a significant luminosity decrease during a few hours run. We present in this note a new method of luminosity leveling, based on the on-line adjustment of the crossing angle, while keeping the optics unchanged. It is implemented using the D0 dipole of a possible Early Separation Scheme and an orbit corrector. The whole scheme is confined in the experimental drift space. It should be operationally simple as it avoids most complicated side effects that other leveling principles would produce

D0 and its integrability

In this paper, we present the performances of the so called D0 scheme with respect to the LHC luminosity gain and its integrability scenarios in the detectors’ area. In particular we propose some possible positions for the D0 and we present the corresponding integrated field requested. The positions are the product of a very preliminary interactions of the physicists’ detectors. In the integration’s feasibility, the beam–beam effect in the new crossing scheme and the impact of the solenoidal magnetic field of the detectors on the D0 are considered

Luminosity leveling with angle

The very high luminosity foreseen for the LHC luminosity upgrade entails in all cases a significant luminosity decrease during a few hours run. We present in this note a new method of luminosity leveling, based on the on-line adjustment of the crossing angle, while keeping the optics unchanged. It is implemented using the D0 dipole of a possible Early Separation Scheme and an orbit corrector. The whole bump is confined in the experimental drift space. It should be operationally simple as it avoids most complicated side effects that other leveling principles would produce