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The physics programme and the design are described of a new collider for particle and nuclear physics, the Large Hadron Electron Collider (LHeC), in which a newly built electron beam of 60 GeV, to possibly 140 GeV, energy collides with the intense hadron beams of the LHC. Compared to the first ep collider, HERA, the kinematic range covered is extended by a factor of twenty in the negative four-momentum squared, Q 2 , and in the inverse Bjorken x, while with the design luminosity of 10 33 cm −2 s −1 the LHeC is projected to exceed the integrated HERA luminosity by two orders of magnitude. The physics programme is devoted to an exploration of the energy frontier, complementing the LHC and its discovery potential for physics beyond the Standard Model with high precision deep inelastic scattering measurements. These are designed to investigate a variety of fundamental questions in strong and electroweak interactions. The LHeC thus continues the path of deep inelastic scattering (DIS) into unknown areas of physics and kinematics. The physics programme also includes electron-deuteron and electron-ion scattering in a (Q 2 1/x) range extended by four orders of magnitude as compared to previous lepton-nucleus DIS experiments for novel investigations of neutron's and nuclear structure, the initial conditions of Quark-Gluon Plasma formation and further quantum chromodynamic phenomena. The LHeC may be realised either as a ring-ring or as a linac-ring collider. Optics and beam dynamics studies are presented for both versions, along with technical design considerations on the interaction region, magnets including new dipole prototypes, cryogenics, RF, and further components. A design study is also presented of a detector suitable to perform high precision DIS measurements in a wide range of acceptance using state-ofthe art detector technology, which is modular and of limited size enabling its fast installation. The detector includes tagging devices for electron, photon, proton and neutron detection near to the beam pipe. Civil engineering and installation studies are presented for the accelerator and the detector. The LHeC can be built within a decade and thus be operated while the LHC runs in its high-luminosity phase. It so represents a major opportunity for progress in particle physics exploiting the investment made in the LHC.

Abstract. The first phase of the ATHENA (AnTiHydrogEN Apparatus) experiment is devoted to the study of cold antihydrogen production.The apparatus includes an antiproton capture trap designed to trap and to cool antiprotons coming from the CERN Antiproton Decelerator (AD). The antiproton cooling is achieved by means of the collisional interaction with a cold cloud of trapped electrons. The electron plasma is loaded in the trap before the antiproton capture by means of a small-size heated filament and cooled to sub-eV temperatures by cyclotron radiation.We report some measurements devoted to the characterization of the electron plasma. The ATHENA apparatus design does not allow the use of complex diagnostic; therefore the plasma properties are obtained using electrostatic wall probes, radio-frequency diagnostic, and dumping the electrons onto a charge collector. A simple experimental method to obtain an estimate of the electron plasma radius is discussed.

We have developed a new method, based on the ballistic transfer of preaccumulated plasmas, to obtain large and dense positron plasmas in a cryogenic environment. The method involves transferring plasmas emanating from a region with a low magnetic field (0.14 T) and relatively high pressure (10 ÿ9 mbar) into a 15 K Penning-Malmberg trap immersed in a 3 T magnetic field with a base pressure better than 10 ÿ13 mbar. The achieved positron accumulation rate in the high field cryogenic trap is more than one and a half orders of magnitude higher than the previous most efficient UHV compatible scheme. Subsequent stacking resulted in a plasma containing more than 1:2 10 9 positrons, which is a factor 4 higher than previously reported. Using a rotating wall electric field, plasmas containing about 20 10 6 positrons were compressed to a density of 2:6 10 10 cm ÿ3 . This is a factor of 6 improvement over earlier measurements.

The electron-positron collider DAÈNE, the Italian È factory, has been recently upgraded in order to implement an innovative collision scheme based on large crossing angle, small beam sizes at the crossing point, and compensation of beam-beam interaction by means of sextupole pairs creating a ''crab-waist'' configuration in the interaction region. Experimental tests of the novel scheme exhibited an increase by a factor of 3 in the peak luminosity of the collider with respect to the performances reached before the upgrade. In this Letter we present the new collision scheme, discuss its advantages, describe the hardware modifications realized for the upgrade, and report the results of the experimental tests carried out during commissioning of the machine in the new configuration and standard operation for the users. DOI: 10.1103/PhysRevLett.104.174801 PACS numbers: 29.27.Bd, 29.20.db, 29.27.Eg Pushing the luminosity of storage-ring colliders to unprecedented levels opens up unique opportunities for precision measurements of rare decay modes and extremely small cross sections, which are sensitive to new physics beyond the standard model.In high luminosity colliders with conventional collision schemes the key requirements to increase the luminosity are: very small vertical beta function y at the interaction point (IP), high beam intensity and large horizontal emittance " x and beam size x . However, y cannot be much smaller than the longitudinal rms bunch size (bunch length) z without incurring the ''hour-glass'' effect. Unfortunately, it is very difficult to shorten the bunch in a high current ring without exciting collective instabilities. Even then, the large beam current may result in high power losses, beam instabilities and dramatic increase of the wallplug power. These problems can be overcome with the recently proposed crab-waist (CW) scheme of beambeam collisions [1,2] where a substantial luminosity increase can be achieved without bunch length reduction and with moderate beam currents.The CW scheme has been successfully tested at the electron-positron collider DAÈNE, the Italian È factory [3,4] operating at the energy of 1020 MeV in the center of mass. After an upgrade including the implementation of this novel collision scheme, the specific luminosity at low beam currents has been boosted by more than a factor of 4, while the present peak luminosity is a factor of 3 higher than the maximum value obtained with the original configuration based on the standard collision scheme.The successful test has provided the opportunity to continue the DAÈNE physics program. Moreover, the advantages of the crab-waist collision scheme have triggered several collider projects exploiting its potential. In particular, physics and accelerator communities are discussing new projects of a SuperB factory [5,6] and a SuperTau-Charm factory [7] with luminosities about 2 orders of magnitude beyond those achieved at the present B-[8] and Tau-charm factories [9].In this Letter we briefly introduce the CW concept, shortly discuss ...