Fast Timing System Research Articles

Systematic investigation of time walk and time resolution characteristics of CAEN digitizers V1730 and V1751 for application to fast-timing lifetime measurement

The timing performance of the integrated digital constant fraction discriminators of the two digitizer modules V1730 and V1751 from CAEN are systematically investigated with respect to fast-timing lifetime measurements. Systematic and parameter-dependent knowledge of the time walk behavior and the time resolution of the digital constant fraction discriminators is obtained. Understanding these dependencies is crucial for properly calibrating individual fast-timing systems and a comparable investigation of these digitizers was never conducted before. Reference is made to the existing analog standard for fast-timing techniques and recent digital developments. The study shows, that the timing performance of both modules is comparable to other digital fast-timing implementations and established fast-timing setups using analog constant fraction discriminators, but with the added benefit of digital processing. The peculiarities of the modules are pointed out and described. Both digitizer modules were found to be highly effective and user-friendly instruments for modern fast-timing requirements. Best parameter sets for both digitizers as well as best energy application ranges are provided.

Diamond-Like Carbon for the Fast Timing MPGD

The present generation of Micro-Pattern Gaseous Detectors (MPGDs) are radiation hard detectors, capable of detecting effciently particle rates of several MHz/cm2, while exhibiting good spatial resolution (≤ 50 µm) and modest time resolution of 5-10 ns, which satisfies the current generation of experiments (High Luminosity LHC upgrades of CMS and ATLAS) but it is not sufficient for bunch crossing identification of fast timing systems at FCC-hh. Thanks to the application of thin resistive films such as Diamond-Like Carbon (DLC) a new detector concept was conceived: Fast Timing MPGD (FTM). In the FTM the drift volume of the detector has been divided in several layers each with their own amplification structure. The use of resistive electrodes makes the entire structure transparent for electrical signals. After some first initial encouraging results, progress has been slowed down due to problems with the wet-etching of DLC-coated polyimide foils. To solve these problems a more in-depth knowledge of the internal stress of the DLC together with the DLC-polyimide adhesion is required. We will report on the production of DLC films produced in Italy with Ion Beam Sputtering and Pulsed Laser Deposition, where we are searching to improve the adhesion of the thin DLC films, combined with a very high uniformity of the resistivity values.

Performance of a Customized Cryo-Cooling System Designed for the Measurement of the Lifetime of Nuclear Excited States at Cryogenic Temperatures

Theoretical predictions that the lifetime of nuclear excited states can be varied if the nucleus is subjected to a condition that allows multiple coherent emission and re-absorption of gamma photons by the nucleus is of much interest to the nuclear physicists. Therefore, an experiment has been designed to study the possibility of lifetime variation. Based on the theory requirements, lifetime variations can be observed when the nucleus is cooled to cryogenic temperatures. Both the cryo-cooling system and the fast timing system have been developed. In the current work, the design, operation and performance of the developed cryo-cooling system is discussed. Furthermore, the effect of operating the cryo-cooling system on the gamma detection system was also studied. The cooling system has been observed to be capable of cooling the radioactive source down to 38 K. Temperature fluctuations of only 0.128% of the selected temperature were observed. This indicates the desired stability of the cooling system. On the other hand, both energy and timing resolution of the detection system were found to be affected by the mechanical vibrations of the cooling system. The effect can be reduced by cushioning the detectors and the remaining minor differences in time resolution can be accounted in the experimental uncertainty budget. Keywords: Cryogenic temperature, Cryo-cooling System, Nuclear State, Lifetime Variation, Fast Timing System, Detectors

The investigation of a new fast timing system based on DRS4 waveform sampling system

Abstract In the study of nuclear structure, the fast timing technique can be used to measure the lifetime of excited states. In the paper, we have developed a new fast timing system, which is made up of two LaBr3:Ce detectors and a set of waveform sampling system. The sampling system based on domino ring sampler version 4 chip (DRS4) can digitize and store the waveform information of detector signal, with a smaller volume and higher timing accuracy, and the waveform data are performed by means of digital waveform analysis methods. The coincidence time resolution of the fast timing system for two annihilation 511 keV γ photon is 200ps (FWHM), the energy resolution is 3.5%@511 keV, and the energy linear response in the large dynamic range is perfect. Meanwhile, to verify the fast timing performance of the system, the 152Gd-21+ state form β+ decay of 152Eu source is measured. The measured lifetime is 45.3(±5.0)ps, very close to the value of the National Nuclear Data Center (NNDC: 46.2((±3.9)ps). The experimental results indicate that the fast timing system is capable of measuring the lifetime of dozens of ps. Therefore, the system can be widely used in the research of the fast timing technology.

A discrete-time analog for coupled within-host and between-host dynamics in environmentally driven infectious disease

In this paper, we establish a discrete-time analog for coupled within-host and between-host systems for an environmentally driven infectious disease with fast and slow two time scales by using the non-standard finite difference scheme. The system is divided into a fast time system and a slow time system by using the idea of limit equations. For the fast system, the positivity and boundedness of the solutions, the basic reproduction number and the existence for infection-free and unique virus infectious equilibria are obtained, and the threshold conditions on the local stability of equilibria are established. In the slow system, except for the positivity and boundedness of the solutions, the existence for disease-free, unique endemic and two endemic equilibria are obtained, and the sufficient conditions on the local stability for disease-free and unique endemic equilibria are established. To return to the coupling system, the local stability for the virus- and disease-free equilibrium, and virus infectious but disease-free equilibrium is established. The numerical examples show that an endemic equilibrium is locally asymptotically stable and the other one is unstable when there are two endemic equilibria.

The Generalized Centroid Difference method for lifetime measurements viaγ-γcoincidences using large fast-timing arrays

A novel method for direct electronic “fast-timing” lifetime measurements of nuclear excited states via γ-γ coincidences using an array equipped with N very fast high-resolution LaBr3(Ce) scintillator detectors is presented. The generalized centroid difference method provides two independent “start” and “stop” time spectra obtained without any correction by a superposition of the N(N – 1)/2 calibrated γ-γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ-γ cascade and the centroid difference as the time shift between the centroids of the two time spectra provides a picosecond-sensitive mirror-symmetric observable of the set-up. The energydependent mean prompt response difference between the start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing array mean γ-γ zero-time responses can be determined for 40 keV < Eγ < 1.4 MeV with a precision better than 10 ps using a 152Eu γ-ray source. The new method is described with examples of (n,γ) and (n,f,γ) experiments performed at the intense cold-neutron beam facility PF1B of the Institut Laue-Langevin in Grenoble, France, using 16 LaBr3(Ce) detectors within the EXILL&FATIMA campaign in 2013. The results are discussed with respect to possible systematic errors induced by background contributions.

Stability Analysis of a Vision-Based UAV Controller

The stability analysis of a vision-based control strategy for a quad rotorcraft UAV is addressed. In the present application, the imaging sensing system provides the required states for performing autonomous navigation missions, however, it introduces latencies and time-delays from the time of capture to the time when measurements are available. To overcome this issue, a hierarchical controller is designed considering a time-scale separation between fast and slow dynamics. The dynamics of the fast-time system are stabilized using classical proportional derivative controllers. Additionally, delay frequency and time domain techniques are explored to design a controller for the slow-time system. Simulations and experimental results consisting on a vision-based road following task are presented.

The generalized centroid difference method for picosecond sensitive determination of lifetimes of nuclear excited states using large fast-timing arrays

A novel method for direct electronic “fast-timing” lifetime measurements of nuclear excited states via γ–γ coincidences using an array equipped with N∈N equally shaped very fast high-resolution LaBr3(Ce) scintillator detectors is presented. Analogous to the mirror symmetric centroid difference method, the generalized centroid difference method provides two independent “start” and “stop” time spectra obtained by a superposition of the N(N−1)γ–γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ–γ cascade. Provided that the energy response and the electronic time pick-off of the detectors are almost equal, a mean prompt response difference between start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing arrays mean γ–γ time-walk characteristics can be determined for 40keV<Eγ<1.3MeV with an accuracy less than 5ps using a 152Eu γ-ray source. Due to reduction and cancellation of many possible systematic errors, the lifetime determination limit of the method over the total dynamic range is mainly determined by the statistics. The setup of an N=4 detector fast-timing array delivered an absolute time resolving power of 3ps for 10000 γ–γ events per total fast timing array start and stop time spectrum. The new method is tested over the total dynamic range by the measurements of known picosecond lifetimes in standard γ-ray sources.

Fast timing: Lifetime measurements with LaBr3 scintillators

In order to perform half-life measurements at Alto, we developed a fast-timing setup using fast scintillators : LaBr3. The main components of our setup and their characteristics (timing properties) are presented. The resulting time resolution, obtained after optimization, and measured off-line with radioactive sources is discussed. This set-up was tested on-line by measuring using the slope method half-lives of 137–139Cs levels fed by the β− decay of 137–139Xe. The neutron-rich Xe nuclei were produced by 238U photofission using, at low intensity, the electron beam and the line of the future facility ALTO. Our results show the ability of such a fast-timing system to measure half-lives lower than the total time resolution. Off-line and on-line results are discussed.

Fast triggers for a proton injector at PEFP

A fast timing system has been developed to control transistor transistor logic (TTL) trigger signals which are used to extract the pulsed proton beam from an ion source with the precision of less than submicro seconds. The system has been designed to set a delay and duty of the pulses, respectively, and prohibit the beam pulse by an external interlock signal. The system is based on VME which is composed of VME CPU and fast I/O boards with fan-out modules. The software of the system has been developed by the record/device supports and channel access in the core of the EPICS environments. In the paper, we describe software configurations and hardware drivers.

Identifying damage using local flow variation method

In this paper, a damage identification method called local flow variation is introduced. Itis a practical implementation of a phase space warping concept. A hierarchicaldynamical system is considered where a slow-time damage process causes drifts inthe parameters of a fast-time system describing the measurable response of astructure. The method is based on a hypothesis that the probability distributionfunction of the fast-time trajectory in its phase space is a function of a damagestate. In this method, an ensemble of estimated expectations of a trajectory indifferent locations of the reconstructed phase space is used as a damage featurevector. Using these feature vectors, damage identification is realized by a smoothorthogonal decomposition. An experiment is conducted to validate the method. Atwo-dimensional slow-time damage process is identified from experimental fast-time data.Although damage identification results from the local flow variation are not asaccurate as those from the direct application of phase space warping trackingfunctions, the required computation time is about two orders of magnitude shorter.

The TRISTAN timing system

The TRISTAN accelerator complex comprises four accelerators: a 200 MeV electron linac for positron production, a 2.5 GeV linac, an 8 GeV accumulation ring (AR) and a 30 GeV main ring (MR). The TRISTAN timing system is divided into fast and slow timing systems. The fast timing system supplies timing signals (fast timing) for devices whose operation is synchronized with bunched beams from either the linac or the AR. These signals are also used in various beam monitors and beam feedback systems. The slow timing system generates trigger signals (slow timing) in order to achieve synchronization between the magnetic field and the rf accelerating voltage of the AR or MR. These triggers are also used for the automatic operation of machines. The TRISTAN timing system fulfills the following features with the required flexibility and extensibility while in the operation mode: 1. (1) the linac gun trigger signals and the AR revolution clock are synchronized within ∼ 100 ps in timing accuracy, and a short pulse (∼ 1.5 ns) from the linac is injected and accumulated into an arbitrarily selected bucket of AR for a long time; 2. (2) bucket matching between the AR and MR is achieved within ± 6 ps in timing accuracy and a single bunched beam from the AR is injected into an arbitrarily selected bucket of the MR; 3. (3) the slow timing system manages the operation mode of the AR and MR with both flexibility and extensibility; 4. (4) the synchronization signals are transmitted through coaxial cables over a circumference of 3 km from the main control room.

Technology Update on Fast Plastic Scintillators for Medical Applications

Plastic scintillators appear to have potential utility in three research areas related to nuclear medicine: (1) high count rate applications in general, (2) positron camera applications, and (3) positron source localization through measurement of relative arrival times of annihilation quanta at two co-linear detectors. These three areas of applicability depend on improvement in three specific areas of plastic scintillator technology: (a) development of plastics with very fast decay times, (b) development of plastics with greatly improved high energy photon detection efficiencies (high-Z loaded plastics), and (c) improvement of fast timing system capabilities. The three preceding areas of improvement are discussed.