From narrow to wide band normalization for orbit and trajectory measurements

The beam orbit measurement (BOM) of the LEP collider makes use of a narrow band normalizer (NBN) based on a phase processing system. This design has been working fully satisfactory in LEP for almost 10 years. Development work for the LHC, requiring beam acquisitions every 25 ns, has led to a new idea of a so-called "Wide Band Normaliser" (WBN) which exploits most of the P.U.'s differentiated pulse spectrum. In the WBN the beam position information is converted into a time difference between the zero crossing of two recombined and shaped electrode signals. A prototype based on the existing NBN unit has been developed and tested to prove the feasibility of this new idea. For this the B.P. filters and the 90° hybrids are replaced by L.P. filters and delay lines

A new wide band time normaliser circuit for bunch position measurements with high bandwidth and wide dynamic range

Trajectory and closed orbit measurements are vital for commissioning and operation of accelerators. With the push for high luminosities at modern colliders, the azimuthal bunch distribution becomes very complex, so that various phenomena (beam-beam forces, wake fields) strongly affect the orbits of individual bunches. Hence a system with high bandwidth capable of measuring the transverse position of any bunch is desirable. With the current techniques a bandwidth above 100 MHz can only be achieved by individual integration and digitisation of the pick-up signals. The drawback of such an approach is the limited dynamic range of typically 30 dB. In the context of the development of an orbit system for the LHC at CERN a high bandwidth could be achieved by extending the principle of phase normalisation to a wide band time normalisation of the position monitor signals. The circuit described in this paper (Wide band time normalizer) combines the signals of two pick-up electrodes with different delays and converts the beam position information into a pulse width modulation of the digital output signal. This way a bandwidth of more than 40 MHz and a dynamic range of about 50 dB could be achieved. The paper introduces the requirements for the LHC orbit system, compares various technical solutions and finally explains the working principle of the wide band time normalizer including some laboratory tests results

The Measurement of Chromaticity via a Head-Tail Phase Shift

The most common method of measuring the chromaticities of a circular machine is to measure the betatron tune as a function of the beam energy and then to calculate the chromaticity from the resulting gradient. Even as a simple difference method between two machine energies this method does not allow instantaneous measurements, for instance during energy ramping or beta squeezing. In preparation for the LHC a new approach has been developed which uses the energy spread in the beams for a chromaticity measurement. Transverse oscillations are excited with a single kick and the chromaticity is calculated from the phase difference of the individually sampled head and tail motions of a single bunch. Using this method the chromaticity can be calculated using the data from only one synchrotron period (about 15-50 msec in the case of the LHC). This paper describes the theory behind this technique, two different experimental set-ups and the results of measurements carried out in the SPS

The second generation of optimized beam orbit measurement (BOM) system of LEP: hardware and performance description

The BOM System with its 504 Beam Position Monitors and 40 Processing Electronics Stations, distributed along the 27 km of the LEP tunnel, has been optimized for all beam conditions and modes of operation. The description of the Beam Position Monitors (or PU) behavior in the tunnel is given. The guiding approaches for obtaining both main aspects of the critical BOM performances were: a) high reliability, since most of the electronics is not accessible during operation, and b) resolution, precision and stability of the signal processing equipment for the management of the LEP optics, polarization and energy calibration. The finalized analog signal processing chains, both Wide-Band and Narrow-Band, are described. Since local memories allow for the recording of data at each bunch passage during more than 1000 revolutions, it can be followed by a powerful digital signal processing allowing for many modes of beam observation. Examples are presented of beam and machine behavior studies. The BOM System has been a key instrument for the success of LEP operation

First Beam Tests for the Prototype LHC Orbit and Trajectory System in the CERN-SPS

The first beam tests for the prototype LHC orbit and trajectory system were performed during the year 2000 in the CERN-SPS. The system is composed of a wide-bande time normaliser, which converts the analogue pick-up signals into a 10 bit position at 40 MHz, and a digital acquisition board, which is used to process and store the relevant data. This paper describes the hardware involved and presents the results of the first tests with beam

Application of monoclonal antibodies in quantifying fungal growth dynamics during aerobic spoilage of silage

Proliferation of filamentous fungi following ingress of oxygen to silage is an important cause of dry matter losses, resulting in significant waste. In addition, the production of mycotoxins by some filamentous fungi pose a risk to animal health through mycotoxicosis. Quantitative assessment of fungal growth in silage, through measurement of ergosterol content, colony forming units or temperature increase are limiting in representing fungal growth dynamics during aerobic spoilage due to being deficient in either representing fungal biomass or being able to identify specific genera. Here, we conducted a controlled environment aerobic exposure experiment to test the efficacy of a monoclonal antibody-based enzyme linked immunosorbent assay (ELISA) to detect the proliferation of fungal biomass in six silage samples. We compared this to temperature which has been traditionally deployed in such experiments and on-farm to detect aerobic deterioration. In addition, we quantified ergosterol, a second marker of fungal biomass. At 8 d post aerobic exposure, the ergosterol and ELISA methods indicated an increase in fungal biomass in one of the samples with a temperature increase observed after 16 d. A comparison of the methods with Pearson’s correlation coefficient showed a positive association between temperature and ergosterol and both markers of fungal biomass. This work indicates that the technology has potential to be used as an indicator of microbial degradation in preserved forage. Consequently, if developed as an on farm technique this could inform forage management decisions made by farmers, with the goal of decreasing dry matter losses, improving resource and nutrient efficiency and reducing risks to animal health

Space Division Multiplexing in Optical Fibres

Optical communications technology has made enormous and steady progress for several decades, providing the key resource in our increasingly information-driven society and economy. Much of this progress has been in finding innovative ways to increase the data carrying capacity of a single optical fibre. In this search, researchers have explored (and close to maximally exploited) every available degree of freedom, and even commercial systems now utilize multiplexing in time, wavelength, polarization, and phase to speed more information through the fibre infrastructure. Conspicuously, one potentially enormous source of improvement has however been left untapped in these systems: fibres can easily support hundreds of spatial modes, but today's commercial systems (single-mode or multi-mode) make no attempt to use these as parallel channels for independent signals.Comment: to appear in Nature Photonic

The Wide Band Normaliser: a New Circuit to Measure Transverse Bunch Position in Accelerators and Colliders

In the framework of LHC developments a new idea has emerged to measure transverse beam position, which combines the simplicity and reliabilty of the LEP system with a higher bandwidth. This new system, called "the wide band normaliser", makes use of pick-up signals directly and employs delay lines for the normalisation function. The paper descibes in detail the working principle and gives performance estimates based on computer simulations and test measurements