Entwicklung eines universellen Lambshift-Polarimeters für polarisierte Atomstrahl-Targets wie an ANKE/COSY

Since 1994 a Lamb-shift polarimeter (LSP) for the fast and precise measurement of the polarization of an atomic beam was designed, built and tested at the Institut für Kernphysik of the Universität zu Köln. This universal polarimeter can be used to develop a atomic beam polarized ion source (like for the Cologne SAPIS project) or to measure the polarization of atomic beam targets (jet or storage cell targets, e.g. at COSY-Jülich). This Lamb-shift polarimeter was tested with an unpolarized beam of protons and deuterons at Cologne and, since the beginning of 2001, at the Forschungszentrum (FZ) Jülich with the polarized atomic hydrogen and deuterium beams from the atomic beam source of the polarized gas target at ANKE ($\textbf{A}$pparatus for $\textbf{N}$ucleon and $\textbf{K}$aon $\textbf{E}$jectiles). This polarized intemal storage-cell gas target will be used in the storage ring COSY ($\textbf{Co}$oler \Sy}nchrotron) in 2003. The polarimeter is based an measuring the ratios of Lyman-$\alpha$ transition intensities after Stark quenching of spinfilter selected Zeeman hyperfine states. The nuclear polarization of the atomic beam is deduced by applying the product of several correction factors calculated from known effects. The total correction amounts to between 1.1 and 1.2 depending an the occupation numbers of the hyperfine states. The nuclear polarization of atomic beams of hydrogen and deuterium is determined with an accuracy of $\le$ 1% within a few seconds for beams of $\sim$ 3 $\cdot$ 10$^{16}$ atoms/s in one hyperfine state. Its error is dominated by the systematic errors of the various correction factors and will be lowered to $\approx$ 0.5% using a recently developed new ionizer. The sensitivity of the polarimeter is such that even for a beam intensity reduced to 10% the polarization could be determined reliably. The new ionizer will lower this sensitivity limit to $\le$ 3%. With this sensitivity it appears feasible to measure the polarization in the planned storage cell of ANKE by extracting a small fraction of the atoms. In addition to these studies of the (de)polarization in a storage cell plans are to study the polarization and fraction of recombined molecules H$_{2}$ and especially D$_{2}$ in such a cell (CELGAS project). At Cologne the LSP will be used to develop the atomic beam source for the SAPIS project ($\textbf{S}$tored $\textbf{A}$toms $\textbf{P}$ulsed $\textbf{I}$on $\textbf{S}$ource). The LSP offers itself as a very good instrument for all polarized gas target installations at storage rings

Large Mass and Chemical Potential Model: A Laboratory for QCD?

We use a model based on the hopping parameter expansion to study QCD at large $\mu$. We find interesting behavior in the region expected to show flavor-color locking.Comment: 3 pages, 4 figures, contribution to Lattice03, v2: Ref. 2 correcte

Polarized Fusion. Can Polarization Help to Increase the Energy Output of Fusion Reactors?

Since more than 60 years scientists are working on the idea to produce energy from nuclear fusion of light particles like the Hydrogen isotopes. In the meantime, the energy output of e.g. tokamak reactors was increased by five orders and modern experiments like JET are approaching the border for energy production. The international ITER collaboration is preparing the first fusion reactor that will produce about ten times more energy, compared to the energy that is needed to run the experiment. Today, the laser-induced inertial fusion reached the same level and experiments at the National Ignition Facility (NIF) in California, USA, demonstrate a ratio between produced and induced energy about one at the end of 2013.1 In parallel, it is discussed since 1970 to use nuclear polarized fuel to increase the total cross sections of the different fusion reactions.2 The energy gain of fusion reactors does not depend linearly on the total cross section. Depending on the different concepts for nuclear fusion, magnetic confinement or inertial fusion, the energy gain This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 3.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. 1660112-1 Int. J. Mod. Phys. Conf. Ser. 2016.40. Downloaded from www.worldscientific.com by UNIVERSITY OF FERRARA on 04/19/16. For personal use only. R. Engels & G. Ciullo is improved above average. M. Temporal et al. have shown, e.g., that the energy gain of laser-induced inertial fusion might be increased by a factor four, or that the necessary laser power can be reduced by 20 %, if the nuclear fuel was polarized before.3 The downsized laser power will reduce the costs of the corresponding project by a reasonable amount. In addition, the differential cross sections can be modified so that it will be possible to focus the ejectiles, e.g. the neutrons, on special wall areas. In a tokamak this can be used to concentrate the neutron flux to special outer parts of the blanket, where the cooling can be improved and the neutrons be used for Tritium production via the exothermic reaction 6Li+n → 4He+t.4 At the same time, less cooling is needed for the inner parts of the blanket that allows to bring the magnetic field coils closer to the fusion plasma. The increased magnetic field in the plasma will increase the energy gain additionally. Another option of polarized fuel is a new kind of plasma diagnostic inside a tokamak. In combination with modern Nuclear Magnetic Resonance technologies (NMR) anisotropies in the plasma can be measured to learn more about the different plasma mode

Polarized Fusion. Can Polarization Help to Increase the Energy Output of Fusion Reactors

For more than 50 years it has been discussed to increase the gain of nuclear fusion reactors with the use of polarized fuel. For example, the total cross secti ons of the most interesting fusion reactions d+ t ! 4 He+n or 3 He+d ! 4 He+p are increased by 50% if the spins of both incoming particles are aligned. This effect will increase the energy output of a fusion reactor more than linearly, e.g. by a factor 4. However, before polarized fuel can be used for energy production in the different types of reactors, a number of questions must be answered. In this contribution we give an overview on our various activities in this field of res earch

Polarized Proton Beams from Laser-induced Plasmas

We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the PIC simulation code VLPL to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circular polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM/Shanghai.Comment: 7 pages, 7 figure

Simulation of Polarized Beams from Laser-Plasma Accelerators

The generation of polarized particle beams still relies on conventional particle accelerators, which are typically very large in scale and budget. Concepts based on laser-driven wake-field acceleration have strongly been promoted during the last decades. Despite many advances in the understanding of fundamental physical phenomena, one largely unexplored issue is how the particle spins are influenced by the huge magnetic fields of plasma and, thus, how highly polarized beams can be produced. The realization of laser-plasma based accelerators for polarized beams is now being pursued as a joint effort of groups from Forschungszentrum J\"ulich (Germany), University of Crete (Greece), and SIOM Shanghai (China) within the ATHENA consortium. As a first step, we have theoretically investigated and identified the mechanisms that influence the beam polarization in laser-plasma accelerators. We then carried out a set of Particle-in-cell simulations on the acceleration of electrons and proton beams from gaseous and foil targets. We could show that intense polarized beams may be produced if pre-polarized gas targets of high density are employed. In these proceedings we further present that the polarization of protons in HT and HCl gas targets is largely conserved during laser wake-field acceleration, even if the proton energies enter the multi-GeV regime. Such polarized sources for electrons, protons, deuterons and $^{3}$He ions are now being built in J\"ulich. Proof-of-principle measurements at the (multi-)PW laser facilities PHELIX (GSI Darmstadt) and SULF (Shanghai) are in preparation.Comment: submitted to IO

The ALFA-tag is a highly versatile tool for nanobody-based bioscience applications

Specialized epitope tags are widely used for detecting, manipulating or purifying proteins, but often their versatility is limited. Here, we introduce the ALFA-tag, a rationally designed epitope tag that serves a remarkably broad spectrum of applications in life sciences while outperforming established tags like the HA-, FLAG (R)- or myc-tag. The ALFA-tag forms a small and stable a-helix that is functional irrespective of its position on the target protein in prokaryotic and eukaryotic hosts. We characterize a nanobody (NbALFA) binding ALFA-tagged proteins from native or fixed specimen with low picomolar affinity. It is ideally suited for super-resolution microscopy, immunoprecipitations and Western blotting, and also allows in vivo detection of proteins. We show the crystal structure of the complex that enabled us to design a nanobody mutant (NbALFA(PE)) that permits efficient one-step purifications of native ALFA-tagged proteins, complexes and even entire living cells using peptide elution under physiological conditions

Faster elliptic-curve discrete logarithms on FPGAs

This paper accelerates FPGA computations of discrete logarithms on elliptic curves over binary fields. As a toy example, this paper successfully attacks the SECG standard curve sect113r2, a binary elliptic curve that was not removed from the SECG standard until 2010 and was not disabled in OpenSSL until June 2015. This is a new size record for completed ECDL computations, using a prime order very slightly larger than the previous record holder. More importantly, this paper uses FPGAs much more efficiently, saving a factor close to 3/2 in the size of each high-speed ECDL core. This paper squeezes 3 cores into a low-cost Spartan-6 FPGA and many more cores into larger FPGAs. The paper also benchmarks many smaller-size attacks to demonstrate reliability of the estimates, and covers a much larger curve over a 127-bit field to demonstrate scalability

First evidence of nuclear polarization effects in a laser-induced 3 ⁣^3\mkern-1muHe fusion plasma

Polarized fusion has long ago be proposed as a method to strongly increase the efficiency of fusion reactors. However, the required nuclear spin-polarization conservation in fusion plasmas has never been proven experimentally. Here we report on first experimental data suggesting an increased ion flux from a polarized $^3\mkern-1mu$He target heated by a PW laser pulse as well as evidence for an almost complete persistence of their nuclear-polarization after acceleration to MeV energies. These findings also validate the concept of using pre-polarized targets for plasma acceleration of polarized beams