FAST LUMINOSITY MONITORING USING DIAMOND SENSORS FOR SUPER FLAVOUR FACTORIES

Abstract Super flavor factories aim to reach very high luminosities thanks to a new concept whereby the ultra-low emittance beams collide with a large crossing angle. Fast luminosity measurements are needed as input to luminosity optimisation and feedback in the presence of dynamic imperfections. The required small relative precision can be reached exploiting the very large cross section of the radiative Bhabha process at zero photon scattering angle. The instrumental technique selected to sustain the large particle fluxes is based on diamond sensors to be positioned via moveable stages immediately outside the beam pipe, at locations chosen to minimise the contamination from other particle loss mechanisms

MEASUREMENT OF LOW-CHARGED ELECTRON BEAM WITH A SCINTILLATOR SCREEN

Abstract Measuring electron beam charge lower than 1pC in an accelerator is very challenging since the traditional diagnostics, like Faraday Cup and ICT (Integrated Current Transformer), are limited in resolution to a few pC because of electronic noise. A way to simply measure lower charge would be then to use the linear relation, existing before saturation regime, between the incident charge on a scintillating screen and the total light intensity emitted in response by this screen. Measurements have been performed on PHIL accelerator at LAL, with charge lower than 200pC, with a LANEX screen located close to a Faraday Cup or an ICT. It shows a very good linear response of the screen down to the Faraday Cup and ICT resolution limits ( 3pC for the Faraday Cup and 10pC for the ICT) and therefore allows calibrating the screen for lower charge measurement with an estimated precision of 1% on the linear fit. A noise analysis enables estimating the ultimate screen resolution limit, which is actually dictated by the thermal noise of the CCD imaging the screen, around 10fC. Results of low charge measurements on PHIL will be shown and compared to those coming from a diamond detector installed on PHIL, in order to validate the measurement principle and cross-check both measurements. Such powerful and simple measurement may thereafter be used as a single-shot charge diagnostic for electron beam generated and accelerated by laser-plasma interaction and will be used in the context of the Dactomus projec

Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba3ZnIr2O9

We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba3ZnIr2O9 is a realization of a novel spin-orbital liquid state. Our results reveal that Ba3ZnIr2O9 with Ir5+ (5d(4)) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J = 0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir2O9 dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK

Design of an Interaction Region with Head-On Collisions for the ILC

An interaction region (IR) with head-on collisions is considered as an alternative to the baseline configuration of the International Linear Collider (ILC) which includes two IRs with finite crossing-angles (2 and 20 mrad). Although more challenging for the beam extraction, the head-on scheme is favored by the experiments because it allows a more convenient detector configuration, particularly in the forward region. The optics of the head-on extraction is revisited by separating the e+ and e- beams horizontally, first by electrostatic separators operated at their LEP nominal field and then using a defocusing quadrupole of the final focus beam line. In this way the septum magnet is protected from the beamstrahlung power. Newly optimized final focus and extraction optics are presented, including a first look at post-collision diagnostics. The influence of parasitic collisions is shown to lead to a region of stable collision parameters. Disrupted beam and beamstrahlung photon losses are calculated along the extraction elements