Head Amplifier Research Articles

A Low-Noise Charge Amplifier for the ELENA Trajectory, Orbit, and Intensity Measurement System

A low-noise head amplifier has been developed for the extra low energy antiproton ring beam trajectory, orbit, and intensity measurement system at CERN. This system is based on 24 double-electrode electrostatic beam position monitors installed around the ring. A head amplifier is placed close to each beam position monitor to amplify the electrode signals and generate a difference and a sum signal. These signals are sent to the digital acquisition system, about 50 m away from the ring, where they are digitized and further processed. The beam position can be measured by dividing the difference signal by the sum signal while the sum signal gives information relative to the beam intensity. The head amplifier consists of two discrete charge preamplifiers with junction field effect transistor (JFET) inputs, a sum and a difference stage, and two cable drivers. Special attention has been paid to the amplifier printed circuit board design to minimize the parasitic capacitances and inductances at the charge amplifier stages to meet the gain and noise requirements. The measurements carried out on the head amplifier showed a gain of 40.5 and 46.5 dB for the sum and difference outputs with a bandwidth from 200 Hz to 75 MHz and an input voltage noise density lower than $400~\text {pV}/\surd \text{Hz}$ . Twenty head amplifiers have been already installed in the ring and they have been used to detect the first beam signals during the first commissioning stage in November 2016.

The AD and ELENA orbit, trajectory and intensity measurement systems

This paper describes the new Antiproton Decelerator (AD) orbit measurement system and the Extra Low ENergy Antiproton ring (ELENA) orbit, trajectory and intensity measurement system. The AD machine at European Organization for Nuclear Research (CERN) is presently being used to decelerate antiprotons from 3.57 GeV/c to 100 MeV/c for matter vs anti-matter comparative studies. The ELENA machine, presently under commissioning, has been designed to provide an extra deceleration stage down to 13.7 MeV/c. The AD orbit system is based on 32 horizontal and 27 vertical electrostatic Beam Position Monitor (BPM) fitted with existing low noise front-end amplifiers while the ELENA system consists of 24 \\gls{BPM}s equipped with new low-noise head amplifiers. In both systems the front-end amplifiers generate a difference (delta) and a sum (sigma) signal which are sent to the digital acquisition system, placed tens of meters away from the AD or ELENA rings, where they are digitized and further processed. The beam position is calculated by dividing the difference signal by the sum signal either using directly the raw digitized data for measuring the turn-by-turn trajectory in the ELENA system or after down-mixing the signals to baseband for the orbit measurement in both machines. The digitized sigma signal will be used in the ELENA system to calculate the bunched beam intensity and the Schottky parameters with coasting beam after passing through different signal processing chain. The digital acquisition arrangement for both systems is based on the same hardware, also used in the ELENA Low Level Radio Frequency (LLRF) system, which follows the VME Switched Serial (VXS) enhancement of the Versa Module Eurocard 64x extension (VME64x) standard and includes VITA 57 standard Field Programmable Gate Array Mezzanine Card (FMC). The digital acquisition Field Programmable Gate Array (FPGA) and Digital Signal Processor (DSP) firmware shares many common functionalities with the LLRF system but has been tailored for this measurement application in particular. Specific control and acquisition software has been developed for these systems. Both systems are installed in AD and ELENA. The AD orbit system currently measures the orbit in AD while the ELENA system is being used in the commissioning of the ELENA ring.

Assessment of Interference to the DTT Service Generated by LTE Signals on Existing Head Amplifiers of Collective Distribution Systems: A Real Case Study

The increasing market interest for broadband services led the World Radiocommunication Conference (WRC-07) to allocate the upper part of the UHF band (the so called “digital dividend”) to mobile services. The coexistence of broadcasting and mobile telephony services, i.e., long-term evolution (LTE) in contiguous frequency bands can generate interferences to the reception of digital terrestrial television (DTT) signals; in particular, in the case of collective antenna systems, there is the risk of saturation of the wideband head-end distribution amplifier, due to the high level of the new LTE signals. This paper analyzes such situation in a real environment by means of extensive computer simulations and exploits specific techniques that must be adopted to mitigate such interference.

Acoustic equipment for studying human respiratory sounds

Equipment for recording respiratory and voice sounds from the human body surface is described. An acoustic detector based on an electret microphone and equipped with a stethoscopic head and remote two-channel amplifier of signals of acoustic detectors is designed. The acoustic detectors (preamplifier) are connected to the microphone (linear) input of the remote sound card connected to the personal computer, which processes signals with the use of specialized and universal software.

Picosecond laser amplification system with 93 W high average power

A high average power picosecond laser amplification system with diode-end-pumped Nd:YVO 4 and diode-side-pumped Nd:YAG is described. Laser with power up to 92.7 W, repetition frequency of 73.3 MHz, pulse duration of 26.5 ps, and beam quality of M 2 < 3.5 is generated in the amplification system. Thermal-birefringence-induced depolarization in the Nd:YAG rod laser head amplifier is measured to be 21.9 W though birefringence compensation is performed.

Lumped‐constant‐type optical modulator in the microwave band for digital terrestrial TV broadcasting

AbstractBased on an optical modulator using the electrooptic effect of lithium niobate (LiNbO3) developed and productized in the UHF band (470 to 770 MHz), a lumped‐constant optical modulator with highly sensitive operation at microwave frequencies has been fabricated and tested and the possibility of realizability has been studied with a view to its application to digital terrestrial television broadcasting. The frequency ranges assigned for program transmission links for the digital terrestrial television broadcasting are 6 to 7 GHz and 10 GHz. Since a broad bandwidth (6 to 9 MHz) is available, various technological challenges must be overcome to assure a high C/N. Therefore, the system of the LN optical modulator and the modulation electrode structures have been fundamentally reconsidered, attaining a C/N of about 25 dB as the target at 6 GHz. When the C/N of the input signal is sufficiently high, the C/N of the present system is determined by the input signal voltage to the LN optical modulator, or the optical modulation index. In a real system, a head amplifier with a gain of 20 dB or greater is inserted. Hence, it is considered sufficiently possible to assure a C/N greater than 45 dB (target value) as a system. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(6): 1–9, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20341

Detection of Weak Ultrasound Generated by Nano- and Femtosecond Laser Irradiation Using Piezoelectric Sensors

The possibility of detecting laser-generated ultrasound using slight temperature increases with piezoelectric sensors was investigated. The ultrasound noise generated by nanosecond laser irradiation with a theoretically 1 K temperature-rise was detected clearly by the piezoelectric AE sensors using a built-in head amplifier. The amplitude of the first arrival peaks obtained using the side and front sensors decreased monotonically with the source-sensor separation. The amplitude of ultrasound generated by femtosecond laser irradiation was greater than that by nanosecond laser irradiation with same pulse energy, but no great difference existed in the frequency spectrum of the ultrasonic waveforms.

A study of high-frequency characteristics of write heads with the ac-phase high-frequency magnetic force microscope

We demonstrate frequency characteristic measurement methods of write head with an ac-phase high-frequency magnetic force microscope (HF-MFM). Two measurement methods allow separating the characteristics into electrical ones including the head amplifier and/or interconnects and magnetic ones including head materials. The high spatial resolution ac-phase HF-MFM allows resolving the distribution change of the HF magnetic field with frequency. The relation between HF-MFM and spin-stand data was also investigated. It is thought that HF-MFM measurements can be applied to head performance test before HDD manufacturing.

Measuring simultaneous fluxes from soil of N2O and N2 in the field Using the 15N-gas "nonequilibium" technique.

Our purpose was to measure simultaneous fluxes from soil of both N2O and N2 from the same plot in the field using the 15N-gas "nonequilibrium" technique (i.e., the "Hauck" technique) as used previously for N2. We accommodated analysis of N2O by modifying the head amplifier of our mass spectrometer. Our system accurately measured the 15N enrichments of labeled soil slurries for both N2 and N2O. In the field, we measured flux of N2 and N2O during soil denitrification from a 15N-labeled plot of winter wheat. Nine chamber incubations were conducted over 4 days. N2 flux ranged from below detection limit (<0.022 g x m(-2) x d(-1)) to 0.055 g x m(-2) x d(-1). N2O flux ranged from 0.0002 to 0.0027 g N2O-N x m(-2) x d(-1), with a detection limit of 1.0 x 10(-6) g N2O-N x m(-2) x d(-1). For N2O flux, the 15N-gas technique and gas chromatography technique agreed well (r = 0.98). The 15N enrichment of the soil mineral pool undergoing denitrification, measured nondestructively using the N2O data, dropped from about 0.82 to 0.72 atom fraction 15N over 4 days. Applying the 15N-gas nonequilibrium technique to N2O complements its use for 15N-N2 analysis when studying the relative production of N2O and N2 during denitrification.

A noise-rejecting current amplifier for surface atmospheric ion flux measurements

Large area electrodes are required to determine atmospheric charge fluxes at the earth’s surface. These also act as antennas for power line hum, swamping the small atmospheric electric signals. A battery-powered head-amplifier resolving 0.025 pA is described here, which uses active compensation to substantially cancel the interference, allowing the atmospheric charge fluxes to be resolved in the presence of the interference. The overall response is nominally −100 mV/pA, with 30 dB of 50 Hz rejection. The head amplifier can drive a low impedance line.

1/4 " digital VCR PRML channel and servo processing

An analog partial response maximum likelihood (PRML) channel solution for 1/4 " helical scan VTR is presented. The main building blocks are the head amplifier, the channel IC containing an equalizer, an analog Viterbi detector, clock recovery, automatic track following (ATF) processing, and the corresponding servo and control system.

Evaluation of a bipolar amplifier prototype for silicon strip readout

Abstract Monolithic amplifier circuits have been designed for a head amplifier of the silicon strip detector for the SSC. Experimental chips, including preamplifiers and/or shaping amplifiers were fabricated for practical evaluation. The basic properties of these amplifier chips were examined in terms of pulse response and noise characteristics.

An experimental study for a home-use digital VTR

An experimental digital VTR system is described. A modified DCT (discrete cosine transform) has been developed for this system that needs only one-half the number of multipliers of a conventional DCT, making the hardware scale smaller. A data quantity estimator controls the variable-length coding for completion within a synchronization block, keeping the picture quality high. Three stages of error correction correct more errors and make the probability of miscorrection lower. A high area packing density of 270 Mb/in/sup 2/ is brought about by the use of a low-noise head amplifier, optimized payback signal processing, high-performance magnetic heads and tapes, and a stable tracking to narrow tracks. >

Two channel FM recording for high-definition baseband signals

The two-channel three-segment recording method previously developed for high-definition TV (HDTV) baseband VCR recording is considered. The following aspects of this recording method are investigated: the determination of appropriate FM allocation that matches the characteristics of the tape-head system, the use of rotary head amplifiers and a cosine equalizer, and the correction of characteristic differences between the two channels. A signal-to-noise ratio of over 40 dB has been achieved, and the jitter and moire are imperceptible.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

New video signal-processing LSIs for 8 mm VCRs

A fully integrated bipolar large-scale integration (LSI) signal processing system is described. The system is composed of a single-chip Y/C signal processor, a multifunction charge-coupled device (CCD) comb filter a head amplifier with active equalizers, and a PAL signal processor. About 8800 elements are integrated in the single-chip Y/C signal processor which takes the place of 5 ICs in a conventional video cassette recorder (VCR) system. The design and characteristics of the subsystems are each briefly discussed. >

Dynamic Noise Reduction for High Quality Colour Video

AbstractThe passage of noise through a composite colour video system is considered. Even when a channel is considered “clean”, the noise from head amplifiers moves from one colour channel to the others via “cross-matricing”. Dynamic noise reduction is possible using selective filtering of low information content signals. Filters which incorporate bandwidth switching are considered, using a one or two step approach. The latter is shown to be a more versatile technique.

An inexpensive and reliable electroantennometer with automatic base line offset and drift canceller

ABSTRACT. An inexpensive and reliable electronic device is described which allows measurement, viewing and recording of electroantennogram (EAG) responses. Potential advantages of the device include low cost, simple operation, suitability for bench or field use, built‐in digital readout, separate head amplifier, (+) and (‐) peak value memories, and an exclusive automatic offset and drift cancelling circuit which does not introduce distortion. The device is intended for use in EAG recording, where signals with either rapid or slow depolarizations are being measured, bringing important information in the return‐to‐baseline region, as well as the (+) and (‐) peak values of the EAG.

Analysis of low noise, bipolar transistor head amplifiers for high energy applications of silicon detectors

The properties of bipolar transistors as input devices for low noise head-amplifiers for high energy applications of silicon detectors are discussed. Theoretical and experimental investigations have been carried out for three different configurations of head amplifiers. The results show that under the particular constraints of high energy experiments, the bipolar transistor has some features that make it competitive, if not even superior to the so far widely employed junction field-effect transistors. These constraints are the short processing times that have to be used to cope with the very high counting rates and the large detector capacitances of some experiments. It emerges from the analysis that the bipolar transistor appears to be an attractive input device for head amplifiers intended for large acquisition systems associated with silicon detectors.

Limitations in transformer coupling between radiation detector and head amplifier

Transformer coupling between a nuclear radiation detector and a low noise head amplifier is discussed as a method of improving the signal-to-noise ratio for large capacitance detectors. Such an improvement, however, is considerably lower than expected according to the ideal model because of several limitations and intrinsic noise sources of real transformers. Theoretical and experimental work has been carried on to investigate the effects that limit the performances of real transformer couplings. The way in which their behaviour depends on the type of shaping employed is discussed in detail.

The Closed Orbit Observation System of the CERN Antiproton Accumulator

The Antiproton Accumulator (AA) works at 3.5 GeV/c central orbit momentum, has 5O? m circumference, Q-values around 2 ? and a large dispersion, up to 10 m, over most of its circumference (see ref. 1 for description). Closed orbits have to be measured over the whole range of the very large momentum acceptance (6.5%) and at beam intensities as low as 5 × 109 particles (1.5 mA). Furthermore, the pick-up electrodes have to serve as clearing field electrodes and no straight section space was available for them. They have to be compatible with an UHV of 10-11 Torr and bakeable to 300°C. The AA closed orbit observation system therefore has several unusual features: a wide range of dimensions of the pick-up electrodes, adapted to beam size, up to 70 cm horizontal width; location inside the main magnets and quadrupoles; high input impedance head amplifiers, mounted directly on the vacuum chamber feedthroughs; electronic normalizers to provide the ratio of difference/sum signals; high precision for measuring orbits far from centre. Acquisition, calibration, data treatment and display are performed with the single, stand-alone, controls computer.