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We propose an evolution of the Mu2e experiment, called Mu2e-II, that would leverage advances in detector technology and utilize the increased proton intensity provided by the Fermilab PIP-II upgrade to improve the sensitivity for neutrinoless muon-to-electron conversion by one order of magnitude beyond the Mu2e experiment, providing the deepest probe of charged lepton flavor violation in the foreseeable future. Mu2e-II will use as much of the Mu2e infrastructure as possible, providing, where required, improvements to the Mu2e apparatus to accommodate the increased beam intensity and cope with the accompanying increase in backgrounds.

A Λ hypernuclear spectroscopic experiment, JLab E05-115 was performed at JLab Hall-C in 2009 by the (e, e′K+) reaction. Data of Λ hypernuclei with mass numbers from A = 7 to A = 52 were successfully taken, and the analyses are in progress. A polyethylene (CH2) target was used as a proton target to calibrate energy scales, and to study elementary process of the p(e, e′K+)Λ, Σ0 reaction. A preliminary differential cross section of K+ Λ electro-production at low Q2 [~0.01 (GeV/c)2] and at small kaon angles $${({\rm cos} \theta_{\rm K}^{\rm CM} \sim 0.97)}$$ is reported in the present article.

The missing mass spectroscopy of the HeΛ7 hypernucleus was performed using the Li7(e, e ′K+)HeΛ7 reaction at the Thomas Jefferson National Accelerator Facility Hall C. The Λ- binding energy of the ground-state (1/2+) was determined with a smaller error than that of the previous measurement, being BΛ=5.55±0.10stat.±0.11sys.MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at BΛ=3.65±0.20stat. ±0.11sys.MeV was observed and assigned as a mixture of 3/2+ and 5/2+ states, confirming the "gluelike" behavior of Λ, which makes an unstable state in He6 stable against neutron emission.

Spectroscopy of a Be-10(Lambda) hypernucleus was carried out at JLab Hall C using the (e, e' K+) reaction. A new magnetic spectrometer system (SPL+ HES+ HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of similar to 0.78 MeV (FWHM). The well-calibrated spectrometer system of the present experiment using p(e, e' K+)Lambda, Sigma(0) reactions allowed us to determine the energy levels; and the binding energy of the ground-state peak (mixture of 1(-) and 2(-) states) was found to be B-Lambda = 8.55 +/- 0.07(stat.) +/- 0.11(sys.) MeV. The result indicates that the ground-state energy is shallower than that of an emulsion study by about 0.5 MeV which provides valuable experimental information on the charge symmetry breaking effect in the Lambda N interaction.

Since the 1st generation experiment, E89-009, which was successfully carried out as a pilot experiment of (e,e'K+) hypernuclear spectroscopy at JLab Hall C in 2000, precision hypernuclear spectroscopy by the (e,e'K+) reactions made considerable progress. It has evolved to the 2nd generation experiment, E01-011, in which a newly constructed high resolution kaon spectrometer (HKS) was installed and the “Tilt method” was adopted in order to suppress large electromagnetic background and to run with high luminosity. Preliminary high-resolution spectra of 7 Λ He and 28 Λ Al together with that of 12 Λ B that achieved resolution better than 500 keV(FWHM) were obtained. The third generation experiment, E05-115, has completed data taking with an experimental setup combining a new splitter magnet, high resolution electron spectrometer (HES) and the HKS used in the 2nd generation experiment. The data were accumulated with targets of 7 Li, 9 Be, 10 B, 12 C and 52 Cr as well as with those of CH 2 and H 2 O for calibration. The analysis is under way with particular emphasis of determining precision absolute hypernuclear masses. In this article, hypernuclear spectroscopy program in the wide mass range at JLab Hall C that has undergone three generation is described.

An experiment measuring neutrino-nucleus cross sections has been proposed to the Spallation Neutron Source (SNS) under construction at the Oak Ridge National Laboratory (ORNL). The 1 GeV proton beam, incident on a liquid mercury target, produces a flux of 1015 neutrinos/sec (nu) from the decays of pions and muons that have been brought to rest in the neutron production target. In order to measure the neutrino-nucleus interaction with nuclei, two neutrino detectors will be placed 22 meters from the neutron source. The electronic readout of one of these proposed detectors is discussed in this paper. This detector consists of approximately 20500 straw tubes interlaced with 20 tons of target foils (e.g., iron), and allows the measurement of the charged-current, neutrino-nucleus cross section with

T. Gogami1 ∗, P. Achenbach2, A. Ahmidouch3, I. Albayrak4, D. Androic5, A. Asaturyan6, R. Asaturyan6, O. Ates4, P. Baturin7, R. Badui7, W. Boeglin7, J. Bono7, E. Brash8, P. Carter8, C. Chen4, A. Chiba1, E. Christy4, S. Danagoulian3, R. De Leo10, D. Doi1, M. Elaasar11, R. Ent9, Y. Fujii1, M. Fujita1, M. Furic5, M. Gabrielyan7, L. Gan12, F. Garibaldi13, D. Gaskell9, A. Gasparian3, O. Hashimoto1, T. Horn9, B. Hu14, Ed. V. Hungerford21, M. Jones9, H. Kanda1, M. Kaneta1, S. Kato19, M. Kawai1, D. Kawama1, H. Khanal7, M. Kohl4, A. Liyanage4, W. Luo14, K. Maeda1, A. Margaryan6, P. Markowitz7, T. Maruta1, A. Matsumura1, V. Maxwell7, A. Mkrtchyan6, H. Mkrtchyan6, S. Nagao1, S. N. Nakamura1, A. Narayan15, C. Neville7, G. Niculescu16, M. I. Niculescu16, A. Nunez7, Nuruzzaman15, Y. Okayasu1, T. Petkovic5, J. Pochodzalla2, X. Qiu14, J. Reinhold7, V. M. Rodriguez17, C. Samanta18, B. Sawatzky9, T. Seva5, A. Shichijo1, V. Tadevosyan6, L. Tang4, N. Taniya1, K. Tsukada1, M. Veilleux8, W. Vulcan9, F. R. Wesselmann20, S. A. Wood9, T. Yamamoto1, L. Ya4, Z. Ye4, K. Yokota1, L. Yuan4, S. Zhamkochyan6 and L. Zhu4

A straw tracking detector was proposed for the MECO experiment in order to measure the parameters of the helical trajectory of electrons emitted from stopped muon decays. The events of interest are expected to be embedded in an intense background of both energetic electrons and low-energy protons. A prototype of the proposed detector with its DAQ system was built, tested, and compared to a simulation. The results are reported in this paper. They provide the information required to improve the computer simulation of the MECO experiment, and in general, the design of any high-rate DAQ system that is required to efficiently select minimum ionizing tracks from an environment of highly ionizing particles

A universal SPICE model of the MECO straw detector and its readout system was developed. This model is able to reproduce the signals from the anode wires and the induced charge distribution on the cathode strips. Results from model calculations were compared to test results of a short prototype. Based on the successful reproduction of the experimental results, we used the model to help select parameters to optimize the design of the full scale MECO tracker. This model provides complete signal analysis of the current flows for both anode and cathode readout. In addition, a dual straw model was constructed to calculate the crosstalk and noise between adjacent straws. This paper describes the simulation and test results.

This paper derives equations for the deflection of an anode wire in a proportional straw chamber under electrostatic forces due to misalignments of the wire, deformation of the straw tube surface, and gravity.

Encouraged by the success of the first hypernuclear spectroscopy through the ( e , e ′ K + ) reaction (JLab E89-009), a new improved experiment with a newly developed High resolution Kaon Spectrometer (HKS) and a new configuration of the electron spectrometer is planned at the JLab Hall C. The introduction of the HKS will improve by a factor of two, the energy resolution which was limited by the previous kaon spectrometer. The hypernuclear yield and the signal to noise ratio will be also improved by a factor of 50 and 10, respectively.

A front-end digitizing system is needed forract- the straw tracking-detector of the MECO experiment. This detector has 24,000 channels of time and amplitude readout, and operates in a high singles count-rate environment. This system continuously digitizes the incoming pulses of every channel, using a latency buffer to temporarily hold all digitized information. Channel occupancy information for each event is also sent to a local external logic analyzer, and can become part of the trigger decision. All the stored data in the latency buffer is read with zero-suppression to local RAM upon presentation of a valid trigger. The system can be self-triggered or triggered by a coincidence of the internal occupancy signal with an external gate. The data readout provides sub-nanosecond timing and 6-8 bit amplitude resolution, and the system clock can be varied between 15-75 MHz. This design will be implemented in an ASIC due to the large number of readout channels, the requirement initial parallel data flow due to the high single rates, and the number of memory buffers. The digitizer is to be controlled by a FPGA. This paper presents the conceptual design of this system. We anticipate that the ASIC can be used for many other applications requiring the acquisition of time and waveform signals in high counting rate environments, such as PET, CZT, or other HEP experiments.

Analytic expressions for electron distributions in bremsstrahlung and virtual photon radiation are derived and discussed. The results are used to investigate possible electron scattering geometries which maximize the virtual photon production at forward angles while limiting bremsstrahlung to acceptable values.

In the minimal standard model, MSM, if CP violation is included via the CKM matrix, spin dependent cross sections odd under time-reversal vanish. However these cross sections are not necessarily zero if the MSM is extended to include new CP violating mechanisms, e.g., through the exchange of neutral or charged Higgs bosons. Thus a precision measurement of T-odd total cross sections using polarized beams and targets could be a valuable test of time-reversal asymmetries and their mechanisms.

Since the pioneering experiment E89-009 studying hypernuclear spectroscopy using the (e, e’K+) reaction was completed, two additional experiments, E01-011 and E05-115, were performed at Jefferson Lab. These later experiments used a modified experimental design, the "tilt method", to dramatically suppress the large electromagnetic background, and allowed for a substantial increase in luminosity. Additionally, a new kaon spectrometer, HKS (E01-011), a new electron spectrometer, HES, and a new splitting magnet (E05-115) were added to produce new data sets of precision, high-resolution hypernuclear spectroscopy. All three experiments obtained a spectrum for 12B-Lambda, which is the most characteristic p-shell hypernucleus and is commonly used for calibration. Independent analyses of these different experiments demonstrate excellent consistency and provide the clearest level structure to date of this hypernucleus as produced by the (e, e’K+) reaction. This paper presents details of these experiments, and the extraction and analysis of the observed 12B-Lambda spectrum.

A Lambda hyperon which has a strangeness can be bound in deep inside of a nucleus since a Lambda does not suffer from the Pauli exclusion principle from nucleons. Thus, a Lambda could be a useful tool to investigate inside of a nucleus. Since 2000, Lambda hypernuclear spectroscopic experiments by the (e, e'K+) reaction have been performed at the experimental Hall C in Thomas Jefferson National Accelerator Facility (JLab Hall C). An experiment, JLab E05-115 was carried out to investigate Lambda hypernuclei with a wide mass range (the mass number, A = 7, 9, 10, 12, 52). The latest analysis status of JLab E05-115 experiment is discussed in the present article.

An experiment with a newly developed high-resolution kaon spectrometer and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab. The ground state of a neutron-rich hypernucleus, (Λ)(7)He, was observed for the first time with the (e, e'K+) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The (Λ)(7)He binding energy supplies the last missing information of the A = 7, T = 1 hypernuclear isotriplet, providing a new input for the charge symmetry breaking effect of the ΛN potential.

The trigger for the MEGA detector system is based on signals from single, high-energy photons interacting in one of the three MEGA pair spectrometers. The trigger is divided into a fast and a slow stage. The first stage produces a fast output if a specific pattern of detector hits is observed in the scintillators and high-speed wire chambers of a pair spectrometer. The second, slow-stage interrogates drift chamber hit patterns and provides a veto when the pattern fails a minimal requirement for reconstruction of the hits into a pair of circular orbits. The trigger interacts with the photon detector electronics by gating limited sections of the detector during the read-out of an event. This paper describes the two stage trigger system, the photon detector electronics, and the implementation of the trigger outputs to strobe the data acquisition system. The performance of the trigger is compared to Monte Carlo simulations of the photon detector response.

In this paper we present a systematic study of the momentum resolution of the CEBAF Hall C spectrometers. These are the High Momentum Spectrometer (HMS) and Short Orbit Spectrometer (SOS). This systematic study enables us to point out the dominating sources of the spectrometer resolutions. It demonstrates that such a systematic analysis can provide the information required to optimize the performance of an existing spectrometer system or the design of a new spectrometer system.

This paper describes a large acceptance cylindrical drift chamber detector designed and built for the study of the np → pp π − reaction at neutron beam energies in the range 500–800 MeV. Details of construction, electronics, testing, and detection efficiencies and resolutions are presented.

This paper reports on the design and the test results of a charge division electronic read-out system for a charged particle proportional wire detector. Electronic calibration and probable error analysis of the system are also discussed. Position resolution for the system has been measured to be 4.8-mm FWHM on a wire of 1.8-m length (0.26%, relative). >

The present status of the K + -nuclear scattering problem is discussed, and implications of the new data sets involving K + total, elastic, and quasi-free cross sections are pointed out.

The construction techniques used in the development of a set of large pair spectrometers for the MEGA detector are discussed. These spectrometers consist of carbon-fiber-composit cylinders on which the conversion foils are mounted, and appropriately spaced wire chambers in each layer which track the conversion leptons. Close tolerances on all dimensions are maintained. The detector has been operating well in the stopped muon beam line at LAMPF.

The precision and CW characteristics of the new CEBAF electron accelerator will allow electromagnetic production of hypernuclear spectra with calculated resolutions between 200 and 300 keV. Experiments are planned to exploit this capability. The following paper reviews experimental considerations in the design of hypernuclear electroproduction, and provides estimates of expected rates and backgrounds. This hypernuclear program could begin in early 1996. Although hypernuclei have now been studied for a number of years, progress in the field has been slow because the experimental facilities available for these studies are not yet sufficient to answer some of the more important questions. Indeed, binding energies and decay properties of the light hypernuclei have not been significantly improved over the earlier nuclear emulsion and bubble chamber experi­ ments.0 However in the last decade, new counter techniques have been introduced, and new production mechanisms have been proposed and tested. Thus the promise of new physics now awaits new programs. There are a number of recent reviews on the status of hypernuclear physics. 2> Most of these reviews are connected, more or less, to the expectation that new accelerators or new experimental facilities will be introduced in the near future. Of particular relevance here, is the advent of the experimental program at the Continu­ ous Electron Beam Accelerator Facility, CEBAF, and the related reviews of hyperon electroproduction. 3> As there is no data on electroproduced hypernuclear spectra, and very little on the elementary process,4> P(r, K)A, these reviews concentrate on theoretically predicted spectra and their cross sections. While the calculations are useful in planning experimental programs, they may not completely reflect reality when the actual data become available. With this in mind, and without attempting to reproduce the existing reviews, this paper outlines an experimental view of the electroproduction of hypernuclei. The first section provides a short summary of the known elementary photoproduction process, particularly with respect to the impact of this data on the design of hypernu­ clear experiments. In later sections it discusses the expected results from a proposed set of measurements to be undertaken at CEBAF, and finally discusses the possibility

The binding energy of 7He-Lambda has been obtained for the first time with reaction spectroscopy using the (e, e'K+) reaction at Jefferson Lab's Hall C. A comparison among the binding energies of the A=7 T=l iso-triplet hypernuclei, 7He-Lambda, 7Li*-Lambda and 7Be-Lambda, is made and possible charge symmetry breaking (CSB) in the Lambda-Nucleon potential is discussed. For 7He-Lambda and 7Be-Lamnda, the shifts in binding energies are opposite to those predicted by a recent cluster model calculation, which assumes that the unexplained part of the binding energy difference between 4H-Lambda and 4He-Lambda, is due to the CSB of the Lambda-Nucleon potential. Further examination of CSB in light hypernuclear systems is required both experimentally and theoretically.

The first measurement of proton, pion, and kaon associated fission of Bi nuclei has been performed in a photon energy range 1. 45 < E γ < 1. 55 GeV. The fission probabilities are compared with an inclusive fission probabilities obtained with photons, protons and pions. The fission probability of Bi nuclei in coincidence with kaons is 0. 18 ± 0. 06 which is ∼3 times larger than the proton and pion associated fission probabilities and ∼2 times larger than inclusive ones. The kaon associated excess fission events are explained in terms of bound Λ residual states and their weak nonmesonic decays.

A new experimental search for coherent, neutrinoless, muon‐to‐electron conversion from a muonic atom has been proposed for the Japanese Proton Accelerator, J‐PARC, now under commissioning. The experiment is completing a conceptual design which proposes a single event sensitivity in the branching ratio of lepton number violating to lepton conserving decays of ≈0.26×10−16. This note briefly describes the experiment and its objectives.

Hypernuclear production by the ( e , e ′ K + ) reaction has unique advantages in hypernuclear spectroscopy of the S = − 1 regime. The second-generation spectroscopy experiment on 12C, 7Li and 28Si targets has been recently carried out at JLab Hall C with a new experimental configuration (Tilt method) and also using a new high-resolution kaon spectrometer (HKS). The experiment is described and preliminary results are presented together with the empasis of significance of the ( e , e ′ K + ) reaction for Λ hypernuclear spectroscopy and its future prospects.

It sometimes seems unfortunate that physics is taught from an axiomatic perspective. Which is to say that in the classroom, physical phenomena are derived from a set of axioms, leaving the impression that nature had no other choice in the matter. While this emphasizes mathematical beauty, it hardly does justice to the way physics actually proceeds to discover these postulates. The subject of strangeness in nuclear systems will be introduced with the encouragement that all students review this field from a historical perspective in order to obtain a clearer understanding of the inductive reasoning process that is crucial to the development of natural science. In the late 1940’s and early 1950’s the concept of a strangeness quantum number was not understood [1]. “Strange” particles were observed when an emulsion was exposed to cosmic rays, and these particles seemed to be produced with high probability, yet had long lifetimes (≈ 10−10 s). Thus one could infer that production and decay occurred by different mechanisms, but evidence that these particles were produced as pairs was mixed, so that explanations involving associated production, requiring a new, conserved quantum number were not generally accepted. It was also at this time, 1952, that a serendipitous event, Fig. 1, was seen in a cosmic ray interaction with an emulsion nucleus [2]. The event resulted in a heavy remnant that traveled a long distance before it decayed, releasing substantial energy. At first, it was thought that the remnant contained a bound pion in a nucleus which eventually annihilated. However, when that explanation was found untenable, it was proposed that this remnant contained one of the new “strange” particles. This inductive leap may seem obvious now, but at that time it was a seminal proposal. It occurred because minds were prepared to accept the idea of another baryon having a new, conserved quantum number [3]. After the discovery of the first hypernuclear event, investigators began to explore this new field, although scanning of emulsion detectors was quite

The HKS (Jlab E01-011) experiment on spectroscopy of Λ -hypernuclei using (e, e'K+) reaction was successfully carried out in 2005. This paper gives a brief description of the experiment and its technique and shows some of the preliminary spectra that are still under analysis.

A 16-channel front-end ASIC is designed for pixellated detectors. It consists of a charge-sensitive-preamplifier(CSA), a CR-(RC)2 shaper and a class-AB buffer for each channel. A novel continuous reset scheme for low noise and large linear range is presented. The equivalent feedback resistance can be digitally programmed by 3 decades. The shaper output width can also be adjusted from 1mus to 10mus, allowing it to be used both for low noise and high counting rate applications. The chip is implemented in 0.6mum CMOS process. The ENC is measured to be 1413e+20e/pF @ 1mus pulse width and 1402e+11e/pF @ 10mus pulse width respectively. The large zero-capacitance ENC is dominant by the FETs used as resistors in the shaper. The nonlinearity is less than 1.1% over an input charge range of 0-28fC using 0.1pF feedback capacitor.

The data acquisition architecture for the tracking detector of the MECO experiment will consist of a preamplifier/discriminator feeding a buffered digitizer which will be controlled by programmable logic. The digitizer converts the timing and analog waveform into digital storage for later readout. In order to evaluate this conceptual design, a prototype system was assembled using an existing digitizer chip, which had similar characteristics to the one proposed for MECO. In this prototype system, the event readout sequence and trigger was controlled by a Xilinx FPGA, and gated data events were transferred for further processing to higher levels in the data stream. The system contained 64 input channels divided into four groups of 16 channels, and either anode or cathode signals could be processed. It could be operated in either an internal or external trigger mode. Test results are reported in this paper, including the maximum event rate, the system dead time, and the relationship between the system efficiency and the hitmap selection. Based on these test results, some improvements in the digitizer chip are discussed, and the specifications of our proposed digitizer are presented.

Mega is an experiment to search for the decay μ→eγ. It is designed to test lepton-number conservation in muon decay by a background free measurement in this branching ratio at a sensitivity of a few ×10−13. This paper reports particularly on the design and performance of the MEGA detector, as the lessons learned previously are important when new experiments are proposed which would increase the sensitivity of such a measurement down to a branching ratio on the order of 10−14.

[ital K][sup +]-nucleus double-differential cross sections in the quasielastic region have been measured using a kaon beam with an incident laboratory momentum of 705 MeV/[ital c]. Data are presented for D, C, Ca, and Pb at fixed three-momentum transfers of 290, 390, and 480 MeV/[ital c]. Measurements of the effective number of nucleons are compared with calculations predicted from a semiclassical attenuation model based on the eikonal approximation, and the long nuclear mean free path expected for positive kaons is found, even for lead. An exclusive ([ital K],[ital K][prime][ital p]) spectrum for C at 480 MeV/[ital c] is shown. The characteristics of the exclusive data suggest that protons with zero orbital angular momentum have been detected in coincidence. The inclusive data are described well by local density random phase approximation calculations which include isoscalar [ital N]-[ital N] correlations in the [sigma]-[omega] model.

The binding energy of 7ΛHe has been obtained for the first time with reaction spectroscopy using the (e, e'K+) reaction at Jefferson Lab's Hall C. A comparison among the binding energies of the A = 7 T = l iso-triplet hypernuclei, 7ΛHe, 7ΛLi*and 7ΛBe, is made and possible charge symmetry breaking (CSB) in the ΛN potential is discussed. For 7ΛHe and 7ΛBe, the shifts in binding energies are opposite to those predicted by a recent cluster model calculation, which assumes that the unexplained part of the binding energy difference between 4ΛH and 4ΛHe, is due to the CSB of the ΛN potential. Further examination of CSB in light hypernuclear systems is required both experimentally and theoretically.

This paper presents a brief review of the status of K-meson interactions with nuclei. Emphasis is placed on 1s shell nuclei with representative examples drawn from experiments on heavier nuclear systems. Directions for future developments are discussed.

The np total and annihilation cross sections have been measured from near NN threshold (1880 MeV) to 1940 MeV with RMS resolution ranging from 0.08 MeV (1880 MeV) to 6.7 MeV (1940 MeV). No significant narrow meson structures were seen, with 90% C.L. upper limits of 40–180 mb‐MeV on σT for states with width less than our resolution. Combined with increasing unitarity bounds on σ as one approaches threshold, these limits confine widths of possible predicted states below 1900 MeV to less than ∼1 MeV.

The np total and annihilation cross section have been measured from near NN threshold (1880 MeV) to 1940 MeV with RMS resolution ranging from 0.08 MeV (1880 MeV) to 6.7 MeV (1940 MeV). No significant narrow meson structures were seen, with 90% CL upper limits of 40–180 mb-MeV on σΓ for states with width less than our resolution. Combined with increasing unitarity bounds on σ as one approaches threshold, these limits confine widths of possible predicted states below 1900 MeV to less than ∼ 1 MeV.

This paper presents a brief review of the status of K-meson interactions with nuclei. Emphasis is placed on 1s shell nuclei with representative examples drawn from experiments on heavier nuclear systems. Directions for future developments are discussed.

Hypernuclear spectroscopy with electron beam at JLab Hall C has been studied since 2000. The first experiment, JLab E89-009, demonstrated the possibility of the (e, e′ K+) reaction for hypernuclear spectroscopy by achieving an energy resolution of better than 1 MeV (FWHM). The second experiment, JLab E01-011 employed a newly constructed high resolution kaon spectrometer and introduced a vertically tilted electron arm setup to avoid electrons from bremsstrahlung and Moeller scattering. The setup allowed us to have 10 times yield rate and 4 times better signal to accidental ratio with expected energy resolution of 400 keV (FWHM). The third experiment, JLab E05-115 will be performed in 2009 with employing newly constructed high resolution electron spectrometer and a new charge-separation magnet. With the fully customized third generation experimental setup, we can study a variety of targets up to medium-heavy ones such as 52 Cr .