Abstract:
This note describes the design of the Gate &
BLR Generator, a VMEbus module to generate timing signals for the closed
orbit display (CODD) of the CERN PS machine. Based on a reference frequency
produced by another module, the RF-MUX and Synchroniser, this module produces
gating signals for the analogue integrators used in the PS CODD system.
The length and phase of the outputs with respect to the reference frequency
are programmable over a wide range.
Abstract:
This note describes the design of the RF-MUX and
Synchroniser, a VMEbus module to generate timing signals for the closed
orbit display (CODD) of the CERN PS machine. Based on the machine revolution
frequency, a pick-up signal and timing inputs, it produces a beam-synchronous
reference frequency and a number of acquisition triggers, as needed by
the remainder of the CODD system.
Abstract:
A hybrid coupler is a reciprocal radio-frequency
building block with four ports. Signal power applied to any port is equally
divided between the two adjacent ports, while the remaining port receives
none. Hybrid couplers find many uses in RF circuitry. Our specific application
is the elaboration of sum and difference of the signals produced by an
electrostatic position pick-up in a particle accelerator.
Hybrids qualified as 'Wide-Band' commonly span two octaves of frequency,
and the best ultra-wide-band devices cover about three decades. The hybrid
coupler described here has a useful response from 40kHz to some 400MHz.
Abstract:
This note describes the design of a bipolar gated integrator
with base line restoration. Measurements are presented which show that
non-linearity and noise are below 0.1% of full scale for 100 ns gates.
Useful data can be obtained with gate lengths ranging from 30 ns to several
microseconds. Three integrators and a peak detector, together with a 12-bit
ADC, have been assembled on a single printed circuit board to create a
data acquisition system for the beam position monitors in the TT2 and TT70
transfer lines of the CERN PS accelerator complex.
Abstract:
This module has been developed to exchange data
between the VME-based control system and instrumentation in the PS accelerator
and transfer line tunnels. We needed a simple data communications device,
but a survey of commercially available devices showed a lack of suitable
products. The VMOD-TRX is a piggy-back for use with the JANZ VMOD-IO VME
module, and provides bi-directional high-speed serial data communication
over up to 300m of twisted pair cable. Simple software routines to interface
to user applications are described.
Abstract:
Commonly, passive filters work by reflecting unwanted energy back to
the source. This is sometimes undesirable. The addition of a simple
input matching network can yield a constant input resistance filter,
which absorbs outofband energy, rather than reflecting it. This paper
gives circuits and element values for matching networks for Bessel,
Gaussian and linear phase with equiripple filters of orders 3 to 10.
Abstract:
The head electronics of the PS orbit measurement system no longer
fulfill present day requirements. Its components are ageing under
the influence of radiation, and the signal quality is insufficient
to observe beams with intensities below 1e10 ppb. This note identifies
some opportunities for improvement and proposes a new solution, which
should easily allow observation of Pb53+ ions down to 1e9 charges per
bunch.
Abstract:
The PS is equipped with 40 electrostatic Pick-Ups (PUs), constituting
the first element in a signal processing chain which allows reconstruction
of the orbit of the beams circulating in the accelerator. The signals
produced by these PUs are ideally a linear function of the position of
the beam with respect to the centre of the vacuum chamber.
This report describes measurements to assess the precision and
linearity of the PU electrodes with the associated sum and difference
circuits.
Abstract:
To assess the quality of the measurements that can be expected from
a new acquisition system for the particle trajectories in the PS
accelerator, some measurements were made using a Libera digital
signal processor recently. This note presents an analysis of the
results.
Abstract:
During the year 2004, extensive tests using a Libera data processor have been made in
order to study its suitability as a building block for a complete PS trajectory and orbit
measurement system. The Libera consists of four fast 12-bit ADCs, a Virtex II Pro FPGA
and a large memory. This note presents some of the results of the analysis of acquisitions
made on a position pick-up in the CERN PS.
Abstract:
We describe the projected new trajectory measurement system for
the CERN PS, currently under design, in which the trajectory of
each particle bunch is calculated on the fly from a continuous
high-rate stream of digitised PU signal samples. The system will
store data for a full acceleration cycle. Multiple clients will
then be able to select subsets of the data for further treatment
and display. Using a prototype of the projected hardware, raw PU
signals have been accumulated during the 2004 run and processed
off-line, validating the algorithms for beam synchronisation and
calculation of trajectories for all current and known future beam
types (subject to pick-up bandwidth limits) in the PS. Records of
the system behaviour, as implemented by the off-line processing
chain and using real pre-recorded pick-up signals, will be shown.
Abstract:
New electronics has been developed for the remote
control of the pick-up electrodes at the CERN Proton
Synchrotron (PS). Communication between VME-based
control computers and remote equipment is via full
duplex point-to-point digital data links. Data are sent and
received in serial format over simple twisted pairs at a
rate of 1 Mbit/s, for distances of up to 300 m. Coupling
transformers are used to avoid ground loops.
The link hardware consists of a general-purpose VME-module, the TRX (transceiver), containing four FIFO-buffered communication channels, and a dedicated control card for each remote station. Remote transceiver electronics is simple enough not to require microcontrollers or processors. Currently, some sixty pick-up stations of various types, all over the PS Complex (accelerators and associated beam transfer lines) are equipped with the new system.
Even though the TRX was designed primarily for
communication with pick-up electronics, it could also be
used for other purposes, for example to form a local area
network.
Abstract:
With the recent re-appearance of Pb ions in the PS, some shortcomings
of the CODD synchronization system came to light. This note describes
the behaviour of the current system, the problems encountered and
a solution to these problems.
Abstract:
Analog-to-digital conversion and its reverse, digital-to-analog conversion,
are ubiquitous in all modern electronics, from instrumentation and
telecommunication equipment to computers and entertainment. We shall
explore the consequences of converting signals between the analog
and digital domains and give an overview of the internal architecture
and operation of a number of converter types. The importance of analog
input and clock signal integrity will be explained and methods to prevent
or mitigate the effects of interference will be shown. Examples will be
drawn from several manufacturers' datasheets.
Abstract:
The CERN Proton Synchrotron has been fitted with a new trajectory
measurement system (TMS). Analogue signals from the forty beam position
monitors are digitized at 125MS/s, and then further treated entirely in
the digital domain to derive the positions of all individual particle
bunches on the fly. Large FPGAs handle all digital processing. The system
fits in fourteen plug-in modules distributed over three half-width cPCI
crates. Data are stored in circular buffers of large enough size to keep
a few seconds-worth of position data. Multiple clients can then request
selected portions of the data, possibly representing many thousands
of consecutive turns, for display on operator consoles. The system
uses digital phase-locked loops to derive its beam-locked timing
reference. Programmable state machines, driven by accelerator timing
pulses and information from the accelerator control system, direct the
order of operations. The cPCI crates are connected to a standard Linux
computer by means of a private Gigabit ethernet segment. Dedicated server
software, running under Linux, knits the system into a coherent whole.
Abstract:
This is a proposal to equip the CERN PS Booster with a trajectory
measurement system along the same lines as was previously done for the
PS. That is, high-speed ADCs convert all BPM signals directly into the
digital domain at a high rate, and individual bunch positions as well as
averaged orbits are calculated on the fly and stored into a large circular
buffer memory. Multiple users may then read the data they are interested
in. The system will make use of modern fast ADCs, large FPGAs and SDRAM.