LEP3: a low-cost, high-luminosity Higgs factory

The discovery of a relatively light Higgs opens up the possibility of circular e+e- Higgs factories. LEP3 is such a machine with emphasis on low cost, since it re-uses most of the LHC infrastructure, including the tunnel, cryogenics, and the two general-purpose LHC experiments Atlas and CMS, with some modifications. The energy reach of LEP3 is 240GeV in the centre of mass, close to the ZH production maximum. Alternative tunnel diameters and locations are possible, including a Higgs factory housed in the UNK tunnel, UNK-L, and a machine located in a new 80 km tunnel in the Geneva region, TLEP, than can further house a very high energy pp collider. The design merits further consideration and a detailed study should be performed, so that LEP3 can be one more option available to the community for the next step in High Energy Physics.Comment: presented on conference "LHC on the March", 20-22 November 2012, IHEP, Protvino, Russi

FCC-ee accelerator parameters, performance and limitations

CERN has recently launched the Future Circular Collider (FCC) study to deal with all aspects of an ambitious post-LHC possible programme. The emphasis of the study is on a 100 TeV proton collider to be housed in a 80-100 km new ring in the Geneva region. An electron machine will also be considered as a possible intermediate first step (FCC-ee). The study benefits from earlier work done in the context of TLEP and has already published a parameter table, to serve as the basis for the work to be done. The study aims to publish a conceptual design report at around 2018. The recent discovery of a light Higgs boson has opened up considerable interest in circular e+e- Higgs factories around the world. FCC-ee is capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from 90 to 350 GeV. This allows the very precise study of the Z, W and H bosons as well as the top quark, allowing for meaningful precision tests of the closure of the Standard Model.Comment: presented at conference ICHEP2014, 37th conference on High Energy Physics, Valencia, 2-9 July 201

Performance limitations of circular colliders: head-on collisions

We review the different performance limitations of circular colliders, namely the limitations of energy reach, maximum attainable luminosity and beam lifetime. This paper considers only head-on collisions. We consider the range of beam energies from 45GeV to 250 GeV and collider circumferences from 20 to 100kms

Mitigating performance limitations of single beam-pipe circular e+e- colliders

Renewed interest in circular e+e- colliders has spurred designs of single beam-pipe machines, like the CEPC in China, and double beam pipe ones, such as the FCC-ee effort at CERN. Single beam-pipe designs profit from lower costs but are limited by the number of bunches that can be accommodated in the machine. We analyse these performance limitations and propose a solution that can accommodate O(1000) bunches while keeping more than 90% of the ring with a single beam pipe.Comment: Poster presented at IPAC'15, Richmond, VA, USA, May 201

Transverse Polarization for Energy Calibration at the Z peak

In this paper we deal with aspects of transverse polarization for the purpose of energy calibration of proposed circular colliders like the FCC-ee and the CEPC. The main issues of such a measurement will be discussed. The possibility of using this method to accurately determine the energy at the WW threshold as well as the Z peak will be addressed. The use of wigglers for reducing long polarization times will be discussed and a possible strategy will be presented for minimising the energy uncertainty error in these large machines.Comment: Talk presented at HF2014, "the 55th ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e+e- Colliders - Higgs Factory", Beijing, 9-12 October 201

The FCC-ee design study: luminosity and beam polarization

The FCC-ee accelerator is considered within the FCC design study as a possible first step towards the ultimate goal of a 100 TeV hadron collider. It is a high luminosity e+e- storage ring collider, designed to cover energies of around 90, 160, 240 and 350GeV ECM (for the Z peak, the WW threshold, the ZH and ttbar cross-section maxima respectively) leading to different operating modes. We report on the current status of the design study, on the most promising concepts and relevant challenges. The expected luminosity performance at all energies, and first studies on transverse polarization for beam energy calibrations will be presented.Comment: Presented at the European Physical Society Conference on High Energy Physics, 22-29 July 2015, Vienna, Austria. arXiv admin note: text overlap with arXiv:1506.00933, arXiv:1501.0685

A Method for Greatly Reduced Edge Effects and Crosstalk in CCT Magnets

Iron-free CCT magnet design offers many advantages, one being the excellent field quality and the absence of multipole components. However, edge effects are present, although they tend to integrate out over the length of the magnet. Many modern accelerator applications, however, require that these magnets are placed in an area of rapidly varying optics parameters, so magnets with greatly reduced edge effects have an advantage. We have designed such a magnet (a quadrupole) by adding multipole components of the opposite sign to the edge distortions of the magnet. A possible application could be the final focus magnets of the FCC-ee, where beam sizes at the entry and exit point of the magnets vary by large factors. We have then used this technique to effectively eliminate cross talk between adjacent final focus quadrupoles for the incoming and outgoing beams.Comment: Poster presented at MT25,25th International Conference on Magnet Technology, Amsterdam, August 27 - September 1, 201

TLEP, first step in a long-term vision for HEP

The discovery of H(126) has renewed interest in circular e+e- colliders that can operate as Higgs factories, which benefit from three unique characteristics: i) high luminosity and reliability, ii) the availability of several interaction points, iii) superior beam energy accuracy. TLEP is an e+e- storage ring of 80-km circumference that can operate with very high luminosity from the Z peak (90 GeV) to the top quark pair threshold (350 GeV). It can achieve transverse beam polarization at the Z peak and WW threshold, giving it unparalleled accuracy on the beam energy. A preliminary study indicates that an 80 km tunnel could be constructed around CERN. Such a tunnel would allow a 100 TeV proton-proton collider to be established in the same ring (VHE-LHC), offering a long term vision.Comment: This is a contribution to the the Snowmass process 2013: Frontier Capabilitie

Comments on "Wall-plug (AC) power consumption of a very high energy e+/e- storage ring collider" by Marc Ross

The paper arXiv:1308.0735 questions some of the technical assumptions made by the TLEP Steering Group when estimating in arXiv:1305.6498 the power requirement for the very high energy e+e- storage ring collider TLEP. We show that our assumptions are based solidly on CERN experience with LEP and the LHC, as well accelerators elsewhere, and confirm our earlier baseline estimate of the TLEP power consumption.Comment: 6 page