The PS 80 MHz cavities

As part of the preparation of the PS as injector for LHC, two new 80 MHz cavities have been designed and built at CERN. Bunches spaced by 25 ns and less than 4 ns long are required at injection into t he SPS. The bunch spacing is obtained with a 40 MHz system installed in the PS in 1996, but the nominal small bunch length will only be obtained with the 80 MHz systems producing a total of 600 kV. Th ese systems also have the capability to accelerate leptons in the PS, providing a total of 400 kV with high duty cycle (25 %). The mechanical design is similar to that of the 40 MHz cavity with many c ommon parts, but cooling water circuits had to be added. The cavity is equipped with an efficient, pneumatically operated, coaxial short-circuit. The power coupling loop has the form of a wide strip t o minimize the ratio of self to mutual inductance. It has a DC insulation permitting multipactor suppression by a bias voltage. The final amplifier is mounted directly onto the cavity. A fast RF feedb ack with a loop gain of 44 dB reduces the Q to about 100. Higher-order-mode dampers designed and built at TRIUMF have been installed

Insegnare nell'era INVALSI

Il forum ha come scopo fare il punto sulle problematiche che condizionano i processi di apprendimento/insegnamento nello scenario delineato dall'introduzione delle prove INVALS

DSP-Based Stepping Motor Drivers for the LHC Collimators

The control electronics of the LHC collimators stepping motors will be located in radiation safe zones up to 800 meters far from the motors. With such cable lengths the standard chopping drivers do not work properly because of the voltage losses on the cable and even more because of the high cable capacitance. The capacitance in fact produces a ringing phenomenon on the driver feedback current that limits the control chopping frequency to the point of being incompatible with the tight EM emissions requirements of the LHC tunnel. In some cases the feedback loop may even become unstable and the driver would fail. The problem was solved by accurately modeling the overall motor-cable system taking into account non-linearities due to hysteresis and eddy currents and by designing an adaptive digital controller, self-tuning to the real cable length. The controller will aim at increasing the chopping frequency to reduce the spectral density of the emissions and at damping the oscillations of the feedback current to avoid instability. In this paper the model of the motor-cable system as well as the digital controller are described. Particular attention is devoted to the hardware implementation based on a TI Cx2000 DSP

Microwave apparatus for gravitational waves observation

In this report the theoretical and experimental activities for the development of superconducting microwave cavities for the detection of gravitational waves are presented.Comment: 42 pages, 28 figure

The UA9 experimental layout

The UA9 experimental equipment was installed in the CERN-SPS in March '09 with the aim of investigating crystal assisted collimation in coasting mode. Its basic layout comprises silicon bent crystals acting as primary collimators mounted inside two vacuum vessels. A movable 60 cm long block of tungsten located downstream at about 90 degrees phase advance intercepts the deflected beam. Scintillators, Gas Electron Multiplier chambers and other beam loss monitors measure nuclear loss rates induced by the interaction of the beam halo in the crystal. Roman pots are installed in the path of the deflected particles and are equipped with a Medipix detector to reconstruct the transverse distribution of the impinging beam. Finally UA9 takes advantage of an LHC-collimator prototype installed close to the Roman pot to help in setting the beam conditions and to analyze the efficiency to deflect the beam. This paper describes in details the hardware installed to study the crystal collimation during 2010.Comment: 15pages, 11 figure, submitted to JINS

Progress with the Upgrade of the SPS for the HL-LHC Era

The demanding beam performance requirements of the High Luminosity (HL-) LHC project translate into a set of requirements and upgrade paths for the LHC injector complex. In this paper the performance requirements for the SPS and the known limitations are reviewed in the light of the 2012 operational experience. The various SPS upgrades in progress and still under consideration are described, in addition to the machine studies and simulations performed in 2012. The expected machine performance reach is estimated on the basis of the present knowledge, and the remaining decisions that still need to be made concerning upgrade options are detailed.Comment: 3 p. Presented at 4th International Particle Accelerator Conference (IPAC 2013

First Results from Commissioning of the Phin Photo Injector for CTF3

Installation of the new photo-injector for the CTF3 drive beam (PHIN) has been completed on a stand-alone test bench. The photo-injector operates with a 2.5 cell RF gun at 3 GHz, using a Cs2Te photocathode illuminated by a UV laser beam. The test bench is equipped with transverse beam diagnostic as well as a 90-degree spectrometer. A grid of 100 micrometer wide slits can be inserted for emittance measurements. The laser used to trigger the photo-emission process is a Nd:YLF system consisting of an oscillator and a preamplifier operating at 1.5 GHz and two powerful amplifier stages. The infrared radiation produced is frequency quadrupled in two stages to obtain the UV. A Pockels cell allows adjusting the length of the pulse train between 50 nanoseconds and 50 microseconds. The nominal train length for CTF3 is 1.272 microseconds (1908 bunches). The first electron beam in PHIN was produced in November 2008. In this paper, results concerning the operation of the laser system and measurements performed to characterize the electron beam are presented