GSI Repository

Schnell, R.

Brinkmann, K.

Kesselkaul, M.

Wohlfahrt, B.

Zaunick, H.

Laser test stand for double-sided silicon microstrip sensors∗R. Schnell†1, K.-Th. Brinkmann1, M. Kesselkaul1, B. Wohlfahrt1, and H.-G. Zaunick11II. Physikalisches Institut, Justus-Liebig-Universita¨t Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, GermanyIntroductionA test stand based on an infrared laser was set up as atool for tests and verifications of double-sided silicon stripdetector modules. It can be used to study prototype as-semblies with silicon sensors. Furthermore, it can be usedto test front-end chips for timing, pile-up behavior andrate capability. This test stand is planned to be used forquality assurance tests of modules of double-sided siliconmicrostrip sensors for the PANDA Micro-Vertex-Detector(MVD) [1]. Systematic and reproducible tests can be donein order to verify the full functionality prior the integrationin the detector. A laser test stand enables a variety of testoptions while being more flexible compared to test beamtimes at accelerator facilities.Laser Test StandThe system is build around a laser with a wavelengthof 1060 nm. Light of this wavelength has an attenuationlength in silicon in the order of 1 mm, therefore electron-hole-pairs are created nearly uniformly inside a sensor withFigure 1: The picture shows the setup. The working areawith the laser and the x-y-stage is housed in a light tightbox lined with black foil. The rack below comprises laserdriver, controller of the x-y-stage and auxiliary compo-nents. The readout components can be seen on the right.∗This work was supported by BMBF (grant no. 05P12RGFP6), JCHP-FFE and HIC for FAIR.† Robert.Schnell@exp2.physik.uni-giessen.dea thickness of several 100µm. Together with the shortpulse length of less than 200 ps (FWHM) it emulates thesignal generation of a charged particle crossing a silicondetector. The external triggering of the laser with a jit-ter better than 40 ps and a minimum time difference of12.5 ns between triggers allows measurements for time res-olution and pile-up behavior. The intensity of the laser canbe adjusted, which relates to different energy depositions.A micro-focus optic at the end of the single-mode opticalfiber allows a minimum beam diameter of 10µm. The laseris moved via an x-y-stage with a travel of 100 x 100 mm2.It features position accuracy and repeatability better than1µm. An additional device allows the manual adjustmentof the z-axis for focusing the laser on the sensor. Themovement of the x-y-stage and the triggering of the laseris software controlled. The readout of the detector mod-ules employs the same VME FPGA-based DAQ system [2]that is used for lab tests with radioactive sources and testbeam times. Figure 1 shows a photograph of the test standstudying a double-sided silicon microstrip sensor bondedto APV25 front-end chips [3].179 180 181 182 183 184 18550100150200250300350400amplitude/ADC countsstrip number  step 4  step 7  step 12  step 16  step 19-100 -50 0 50 100 150 200distance/µmFigure 2: The plots shows the induced charge into differentstrips of a sensor with 50µm strip pitch for various posi-tions of the laser. Each curve illustrates the signal distribu-tion in the strips at one position. Several steps with a stepsize of 5µm were performed.References[1] PANDA Collaboration, arXiv:1207.6581v2 [physics.ins-det], November 2011.[2] R. Schnell et al., JINST 6 (2011) C01008.[3] L. Jones, “APV25-S1: User guide version 2.2”, RAL Micro-electronics Design Group, (2001).GSI SCIENTIFIC REPORT 2014 MU-HADRONS-06DOI:10.15120/GR-2015-1-MU-HADRONS-06 113

Laser test stand for double-sided silicon microstrip sensors

Helmholtz Institute Jena ,

Annual Report 2014

Tanha, M.

Amend, W.

Appelshäuser, H.

Arend, A.

Blume, C.

Dillensenger, P.

Gläßel, S.

Roether, F.

Construction and test of a new CBM-TRD prototype in Frankfurt ∗M. Tanha, W. Amend, H. Appelsha¨user, A. Arend, A. Arend, C. Blume, P. Dillenseger, S. Gla¨ßel, andF. RoetherInstitut fu¨r Kernphysik, Goethe-Universita¨t Frankfurt, GermanyA new TRD prototype based on a thin Multi Wire Pro-portional Chamber (MWPC) without a drift region andwith carbon frame was designed at the Institute for Nu-clear Physics in Frankfurt (IKF) and tested in the test beamat CERN-PS in November 2014. According to this de-sign, two identical real-size prototypes in outer dimen-sions of 586 × 580 × 38.5 mm3 were developed with apitch of 2.5 mm between field and sense wires. Cathode(field) wires made of Cu-Be with a diameter of 80 µm areplaced between gold-plated tungsten anode (sense) wireswith a diameter of 20 µm. The gas gap region, distancebetween entrance window and pad-plane, is 3.5+3.5 mm(see Fig. 1). The chamber were build with the same type ofpad-plane as used in the prototypes from Mu¨nster [1].Figure 1: Schematic drawing of alternating wires, theirpitch and diameters.Applying cathode wires with alternating HV (alternatingwires) has an improving result as it reduces the effect of adeformation of the cathode plane by about a factor of 6,which distorts the gas gain inside the detector via electricfield deformation [2].The MWPC with thin and symmetric geometry(3.5+3.5 mm) provides fast signal collection and effi-cient e/pi separation, which is desired in the CBM exper-iment [3]. The carbon frame, instead of an aluminium orvetronit frame, provides optimum mechanical properties,low thermal expansion, high friction resistance and lowmaterial budget. Figure 2 shows the technical drawing ofthe prototype with the aforementioned components.Figure 3 shows the gas feed-through that is embeddedinside the frame in the corners. Thus, it meets the structuralconditions of the TRD chambers, which will have to bemounted close to each other in the final setup.The data from the CERN-PS test beam in November2014 are currently being analysed. The development of a∗Work supported by BMBF, HIC4FAIR and HGShire.Figure 2: Technical drawing of a TRD prototype with al-ternating wires and carbon frame.Figure 3: The gas feed-through inside the frame.large size (1.0 × 1.0 m2) prototype of the TRD is plannedat the IKF.References[1] C. Bergmann et al., “Test of Mu¨nster CBM-TRD real-sizedetector and radiator prototypes at the CERN PS/T9 beamline”, CBM Progress Report 2014.[2] S. Gla¨ßel, CBM Progress Report 2013, p. 70.[3] E. Hellba¨r, CBM Progress Report 2012, p. 54.GSI SCIENTIFIC REPORT 2014 MU-NQM-CBM-53DOI:10.15120/GR-2015-1-MU-NQM-CBM-53 91

Construction and test of a new CBM-TRD prototype in Frankfurt

Trageser, C.

Brandau, C.

Kozhuharov, C.

Litvinov, Y.

Müller, A.

Nolden, F.

Sanjari, S.

Stöhlker, T.

Commissioning of a continuous broadband data acquisition for Schottkysignals in storage ring experiments at GSI and FAIR∗C. Trageser1,2, C. Brandau1,2, C. Kozhuharov2, Yu.A. Litvinov2,3, A. Mu¨ller1, F. Nolden2, S. Sanjari2,and Th. Sto¨hlker2,4,51Justus-Liebig-Universita¨t, Gießen, Germany; 2GSI-Helmholtzzentrum fu¨r Schwerionenforschung, Darmstadt,Germany; 3Ruprecht-Karls-Universita¨t, Heidelberg, Germany; 4Friedrich-Schiller-Universita¨t, Jena, Germany;5Helmholtz-Institut, Jena, GermanyDuring 2013 and 2014 a modular New Time-Capture(NTCAP) data acquisition system for Schottky signals wasset-up, tested off-line and finally commissioned with beamat the ESR [1, 2]. The main purpose of this device is to un-interruptedly record the RF-signals of storage ring’s Schot-tky probes with high bandwidth for the typical duration ofexperimental runs at storage rings (1 - 4 weeks). Presently,the DAQ is optimized with respect to the new Schottky res-onator with high quality factor that was installed 2010 atthe ESR [3]. The core unit of the NTCAP-DAQ is a vec-tor signal analyzer (VSA, NI PXIe-5663E) that internallyshifts the RF signal by a carrier frequency down to frequen-cies around 0 and decomposes the signal into its in-phase(I) and quadrature (Q) components. With a maximum sam-ple rate of 150 MSamples/s, the VSA is capable to deliverrates up to 7.5 · 107 IQ-Samples/s. The data is recorded asIQ raw-data in the time-domain for further offline process-ing and analysis. The VSA is supplemented by two latch-able fast counter cards (100 kHz readout), a high precisionoscillator, a synchronization module that can use networkor GPS signals, and second digitizer. The details are de-scribed in [2].The applications of such a versatile DAQ are manifold.The Schottky DAQ can run either stand-alone, or synchro-nized and seamlessly integrated into other experimental se-tups: in the latter mode it serves as a ”beam-logbook” insupport of the main experiment and records essential beamparameters such as the composition of stored species downto a single stored ion, the cooling process, frequency, in-tensity or stability of the beam. As a main DAQ it canbe used for experiments on (time-resolved) Schottky massspectrometry (SMS) and β-decay studies of highly chargedions, e.g., [4, 5]. It is proposed by our collaboration toalso utilize the improved time-resolution that is achievedwith the new Schottky resonator [3] for particle detectionin atomic and nuclear reaction studies at the internal targetor the electron cooler.Already in the very first tests with a 400 MeV/u C6+beam at the ESR the high performance of the NTCAP-DAQcould be shown. IQ rates of up to 3.5 · 107 IQ-Samples/scorresponding to a data rate of 140MByte/s could be sus-tained over hours. At the same time the recorded sig-∗Work is supported by BMBF (contracts 06GI911I and06GI7127/05P12R6FAN), by the Helmholtz-CAS Joint ResearchGroup HGJRG-108 and by HIC for FAIR.Figure 1: Single EC-decay of 142Pm60+ (appearance ofsecond trace) recorded with the NTCAP DAQ.nal showed a high dynamic range, low noise and a lowlevel of spurious distortions [2]. By oversampling of thesignal further improve on dynamic range and noise levelcan be achieved offline using decimation or averaging al-gorithms before the Fourier transform into the frequencydomain. In addition to these initial tests, two main ex-periments and several smaller measurements at the ESRwere supported with our NTCAP-DAQ: in a beamtime onlaser spectroscopy of Li-like 209Bi80+ the DAQ was usedto monitor the stability of the ion beam energy during themeasurement and thus to help to improve significance andprecision of this strong-field QED study. The second ma-jor experiment was a two-body β-decay study with singlestored ions of 142Pm60+ aiming at a clarification of the puz-zling observation of a modulated non-exponential decay[6]. Figure 1 shows an example of such a decay demon-strating the capability of our DAQ to also work with weaksignals on a single particle level.References[1] C. Brandau et al., GSI Scientific Report 2013, p. 160.[2] C. Trageser et al., Phys. Scr. T, submitted.[3] F. Nolden et al., Nucl. Instrum. Meth. A 659 (2011), 69.[4] Yu.A. Litvinov and F. Bosch, Rep. Prog. Phys. 74 (2011),016301.[5] F. Bosch et al., Progr. Part. Nucl. Phys. 73 (2013), 84.[6] P. Kienle et al., Phys. Lett. B 726 (2013) 638.APPA-MML-AP-06 GSI SCIENTIFIC REPORT 2014220 DOI:10.15120/GR-2015-1-APPA-MML-AP-06

Commissioning of a continuous broadband data acquisition for Schottky signals in storage ring experiments at GSI and FAIR

Weber, G.

Ding, H.

Bräuning, H.

Heß, R.

Heß, S.

Märtin, R.

Spillmann, U.

Trotsenko, S.

Winters, D.

Precise polarization studies of radiative electron captureG. Weber∗1,2, H. Ding2,3, H. Bra¨uning1, R. Hess1, S. Hess1, R. Ma¨rtin1,2, U. Spillmann1,S. Trotsenko1,2, D. F. A. Winters1, and Th. Sto¨hlker1,2,31GSI, Darmstadt, Germany; 2Helmholtz Institut Jena, Germany; 3IOQ, FSU Jena, GermanyThe capture of electrons into bound states of ions is ofsignificant importance for both experiment and theory inthe fields of atomic and plasma physics as well as for as-trophysics. The capture process is called radiative if it isaccompanied by the emission of a photon that carries awaythe initial electron’s kinetic energy and the binding energyof the final state it is captured into. If the initial electronis considered to be free, the capture process is referred toas radiative recombination (RR), being the time-reversal ofthe photoelectric effect, whereas the capture of a boundelectron is called radiative electron capture (REC) [1].The REC process is a prominent charge-changing pro-cess for fast, highly-charged ions interacting with dedi-cated target materials or with residual gas being present inthe beamlines of accelerators and storage rings. Moreover,when low- to medium-Z targets and heavy, highly-chargedprojectile ions are considered, the to-be-captured electronscan be treated as free particles having a momentum dis-tribution equal to the one of the bound target states. Thisso-called impulse approximation reduces the REC descrip-tion to the RR cross section convoluted with the incidentelectron momentum distribution. Consequently, both theREC and the RR process as well as the photoeffect canbe treated within the same theoretical framework. More-over, when compared to the photoeffect, the RR/REC pro-cess offers several experimental advantages, such as a moreuniform emission pattern due to the partial cancelation ofretardation and Lorentz transformation for a moving emit-ter system and the fact that x-rays, in contrast to electrons,can typically leave the target zone unaffected by secondary-collision effects. These facts motivated various REC mea-surements aiming for a deeper insight into the photoeffectwhile exploiting the advantageous experimental conditionspresent for the study of electron capture into fast, highlycharged ions.A first study of the linear polarization of REC photonswas published in 2006 [2] where a 4× 4 pixel Ge(i) de-tector was used for Compton polarimetry of x-rays emittedin collisions of bare uranium ions with a N2 target at theexperimental storage ring (ESR) of GSI. The experimentalfindings are presented together with theory values in fig-ure 1a. Having only 16 pixels, the relatively low granular-ity of the detector resulted in a poor angular resolution ofthe Compton scattering distribution, which limited the ex-perimental accuracy to an uncertainty between ±5 % and±10 % with respect to the degree of linear polarization.The much higher granularity of a newly developed Si(Li)polarimeter [3](see figure 1b) enables more precise stud-∗ g.weber@gsi.deFigure 1: a) Degree of linear polarization of the radiativeelectron capture (REC) into the K-shell of bare uraniumprojectiles measured with a 4× 4 pixel Ge(i) detector ap-plied as a Compton polarimeter [2]. b) Position distributionof Compton scattered K-REC photons inside the Si(Li) po-larimeter for the capture into bare xenon ions. Data analy-sis with respect to the degree of linear polarization is ongo-ing. The much higher granularity of the new detector is ex-pected to enable significantly more precise measurementscompared to the 16 pixel detector.ies and this instrument was already applied in a series oftest measurements also addressing the REC radiation [4,5].Data analysis is still in progress and we expect an experi-mental uncertainty for these new polarization studies in theorder of ±1 % of the degree of linear polarization. Withregard to future experiments at the new FAIR facility it isworth noting that while the existing ESR is limited to typ-ical ion energies not higher than 400 MeV/u for beams ofheavy ions, the planned high-energy storage ring (HESR)will reach up to approximately 5 GeV/u for bare uranium.With the extended energy range it will become possible toprobe the cross-over effect in the degree of REC photon lin-ear polarization which is predicted to occur at collision en-ergies above 600 MeV/u and for forward emission angles,see the theory data for 800 MeV/u in figure 1a. In terms ofthe photoeffect this feature indicates that the initially boundelectron is no longer preferentially ejected in the directionof the incident photon electric field vector, instead emissionalong the magnetic field vector is dominant.References[1] J. Eichler and Th. Sto¨hlker, Phys. Rep. 439 (2007) 1[2] S. Tashenov et al., Phys. Rev. Lett. 97 (2006) 223202[3] G. Weber et al., JINST 5 (2010) C07010[4] S. Hess et al., J. Phys. Conf. Ser. 163 (2009) 012072[5] S. Hess et al., J. Phys. Conf. Ser. 194 (2009) 012025APPA-MML-AP-10 GSI SCIENTIFIC REPORT 2014224 DOI:10.15120/GR-2015-1-APPA-MML-AP-10

Precise polarization studies of radiative electron capture

Krieg, J.

Chen, C.

Avila, J.

Trautmann, C.

Asensio, M. C.

Toimil Molares, M. E.

XPS measurements on single Bi2Te3 nanowires fabricated by electrodepositionin etched ion-track membranes∗J. Krieg1,2, C. Chen3, J. Avila3, C. Trautmann1,2, M.-C. Asensio3, and M.E. Toimil-Molares†11GSI, Darmstadt, Germany; 2Technische Universita¨t, Darmstadt, Germany; 3SOLEIL Synchrotron, Gif-sur-Yvette,FranceBi2Te3 belongs to a recently discovered new class ofmaterials, called topological insulators (TI), which formconductive surface states while their bulk material is anordinary band insulator. These exotic surface states aregenerated by strong spin-orbit coupling and feature spin-momentum locking of the charge carriers due to time re-versal symmetry. For this reason TI materials are of highinterest for future electronic applications like dissipation-less transport and spintronics [1, 2]. The major challengeto address the surface states is the reduction of the con-centration of residual bulk carriers dominating over thesignal. Nanowires (NWs) of high surface-to-volume ra-tio combined with controllable geometric, crystallographicand morphologic properties are excellent model systems toinvestigate the TI surface states.Here, we present x-ray photoelectron spectroscopy (XPS)studies with sub-micron resolution on individual 100 nmdiameter Bi2Te3 NWs. The NWs are synthesized by elec-trodeposition in etched ion-track templates fabricated by ir-radiating 30 µm thick polycarbonate foils with GeV heavyions at the UNILAC accelerator and selective chemicaletching of the ion tracks in 6 M NaOH at 50 ◦C. Subse-quently, NWs are electrodeposited within the channels atan applied potential of 0 V vs. SCE at 30 ◦C. Details onthe fabrication and characterization are reported in [3].After deposition, the NWs were released from the mem-brane and randomly distributed onto a silicon wafer. Fig-ure 1 displays XPS spectra recorded with an unfocusedbeam, i.e. from the entire substrate, as prepared (red), after15 s (blue) and 15 min (black) of Ar plasma cleaning inUHV. The O and C signals indicating contamination of theBi2Te3 surface by i.e. oxidation, polymer residual, etc., de-crease with increasing cleaning time. After surface prepa-Figure 1: XPS spectra recorded in defocused mode as pre-pared, after 15 s and after 15 min of Ar plasma cleaning.∗Work supported by DFG (No. SPP 1666) and HGS-HIRe† M.E.ToimilMolares@gsi.deration, single NWs were identified in the focused beammode by scanning the area of interest and detecting onlyphotoelectrons of a certain energy (corresponding to Bi orTe). A representative XPS map is presented in fig. 2 a ev-idencing the excellent spatial resolution achieved. SingleNWs can be distinguished from bundles and analysed inmore detail. Figures 2 b and c display two mappings of thesingle NW marked in fig.2 a (black frame) recorded usingTe 55 eV (b) and Bi 68.5 eV (c), respectively. The Te signalis localized on the NW, while Bi signals are detected alsoat larger distances from the NW surface. Further measure-ments are required to understand the origin of these signalsat 68.5 eV in the NW surroundings.In conclusion, the first nano-XPS measurements on 100 nmdiameter Bi2Te3 NWs were successfully performed. Acleaning protocol to obtain highest surface quality was es-tablished. Point XPS spectra along the NWs indicate thatour NWs are of homogeneous elemental composition.Figure 2: XPS mappings of Bi2Te3 NWs: overview (a),single NW recorded by analysing Te (b) and Bi (c) spectra.References[1] C. L. Kane, E.J. Mele, Phys. Rev. Lett. 95, 146802 (2005)[2] M. Konig et al., Science 318, 766 (2007)[3] O. Picht et al., J. Phys. Chem. C 116, 5367-5375 (2012)APPA-MML-MR-16 GSI SCIENTIFIC REPORT 2014268 DOI:10.15120/GR-2015-1-APPA-MML-MR-16

XPS measurements on single Bi$_{2}$Te$_{3}$ nanowires fabricated by electrodeposition in etched ion-track membranes

Dyzynski, M.

Burr, L.

Toimil Molares, Maria Eugenia

Schubert, I.

Synthesis of AuxAg1−x nanowire-networks with controlled composition anddefined wire diameterM. Dyzynski1,2, L. Burr2,3, C. Trautmann2, M. E. Toimil-Molares2, and I. Schubert21Hochschule RheinMain, Ru¨sselsheim, Germany; 2GSI, Darmstadt, Germany; 3Technische Universita¨t Darmstadt,GermanyIn this work, three dimensional AuAg-alloy-nanowire-networks with controlled composition and defined wirediameter were fabricated by electrodeposition in ion-tracketched polymer templates. These structures are very inter-esting for applications in sensorics and catalysis since theyexhibit a very high surface area and are mechanically stabledue to their interconnected nanowires.For the synthesis of the nanowire-networks, we have ir-radiated 30 µm-thin polymer foils at the GSI linear ac-celerator UNILAC with swift heavy ions of initial energy11.4 MeV/u. Each foil is sequentially irradiated four timesunder an angle of 45◦ respective to the polymer surface.The ions damage molecular bonding in the foils and cre-ate cylindrical damage tracks. By chemical etching withaqueous 6-M NaOH solution at 50◦ C these ion tracks aretransformed into nanochannels. Under these etching con-ditions, the etching rate amounts 23 nm/min. By varyingthe etching time between 2 min and 5 min nanochannelswith defined diameter between 60-150 nm were fabricated.After creating a conductive cathode layer by sputteringgold on one side of the foil, nanowires are electrodepositedin the pores. We have deposited AuAg-nanowires usingan electrolyte consisting of 50 mmol KAu(CN)2 and 50mmol KAg(CN)2 in a three-electrode set-up. A Ag/AgClelectrode was used as reference electrode and a platinumcoil as anode. All deposition potentials are given here vs.Ag/AgCl reference. Wet-chemical dissolution of the poly-mer leads to free-standing stable nanowire-networks. Fig.1 shows the SEM image of a network with 100 nm wirediameter.1µm100nmFigure 1: SEM image of a AuAg-nanowire-network with awire diameter of 100 nm.The applied voltage during the deposition was variedto create nanowires with controlled Au:Ag concentrations.Fig. 2 shows details of EDX in SEM spectra including theMα-peak of Au and Lα- and Lβ-peak of Ag. All spec-tra are normalized to the height of the Mα-peak for clarity.Table 1 shows the concentration for networks deposited atvoltages between -0.6 and -0.8 V. For the networks at -Figure 2: EDX spectra of AuAg-alloy-nanowire-networksdeposited at different voltages in the rage between -0.8 and-0.6 V.Networks Parallel arraysPotential/V Au:Ag[%] Au:Ag[%]-0,8 V 50:50 20:80-0,7 V 30:70 --0,6 V 20:80 -Table 1: Au:Ag ratio in the nanowires of networks and par-allel arrays for different deposition potentials.0.8 V the same Au:Ag concentration in the nanowires isfound as present in the electrolyte. In contrast, for arraysconsisting of parallel nanowires a Au:Ag concentration of20:80 was measured at this potential [1]. We attribute thisdifference in wire composition between parallel nanowirearrays and networks to variations in the diffusion process,due to interconnections among pores and the different ef-fective lengths.References[1] I. Alber, “Synthesis and Plasmonic Properties of MetallicNanowires and Nanowire Dimers”, PhD thesis, Ruprecht-Karls-Universita¨t Heidelberg, 2012.GSI SCIENTIFIC REPORT 2014 APPA-MML-MR-17DOI:10.15120/GR-2015-1-APPA-MML-MR-17 269

Synthesis of Au$_x$Ag$_{1-x}$ nanowire-networks with controlled composition and defined wire diameter

Busold, S.

Schumacher, D.

Brabetz, C.

Jahn, D.

Kroll, F.

Deppert, O.

Blazevic, A.

Bagnoud, V.

Roth, Markus

Upgrade of GSI’s laser-driven ion beamline at Z6∗S. Busold1,2, D. Schumacher1, C. Brabetz1, D. Jahn3, F. Kroll4, O. Deppert3, A. Blazevic1,2,V. Bagnoud1,2, and M. Roth31GSI Helmholtzzentrum fu¨r Schwerionenforschung GmbH, Darmstadt, Germany; 2Helmholtz Institut Jena, Germany;3IKP, TU Darmstadt, Germany; 4Helmholtz-Zentrum Dresden - Rossendorf, GermanyThe LIGHT beamlineThe German national collaboration ”LIGHT” (Laser IonGeneration, Handling and Transport, [1]) has implementeda worldwide unique laser-driven proton beamline at GSI.Compact acceleration up to nearly 30 MeV proton ener-gies is possible from the novel plasma source via the TNSAmechanism, which is driven by the PHELIX 100 TW laserbeam. Therefore, at the Z6 experimental area laser intensi-ties of up to 5×1019 W/cm2 are accessible. A pulsed high-field solenoid then provides for the necessary beam colli-mation and energy selection [2] and typically protons withan energy between 8 and 10 MeV are chosen.Furthermore, a radiofrequency (rf) cavity is implementedat 2 m distance to the source for phase rotation of the cre-ated single bunch, which shows a typical energy spreadof around 20% (FWHM around central energy) and highparticle numbers of up to 109. Energy compression of thebunch below 3% was demonstrated in an experimental runin 2013 [3].solenoid 3 gap cavity quadrupole doubletsFigure 1: Simulation (code: TraceWin) of the 7.8 MeV pro-ton beam size (rms) through the current beamline, from thesource up to a new diagnostic chamber at 6 m.For the 2014 campaign, the beamline has been extended bya diagnostic chamber at 6 m distance to the source, two per-manent magnetic quadrupole doublets (50 mm, 25 T/m) forbeam transport, see figure 1, and an optional third doublet(80 mm, 85 T/m and 45 mm, 105 T/m) for final focusing ofthe bunch. The additional space behind the cavity, whichis again used at -90 deg synchronous phase but this time athigher rf power to ’over-focus’ the bunch in longitudinalphase space, compare figure 2, is necessary as drift space∗This work is supported by the Helmholtz Institute Jena.phase@108.4MHz [deg]rel. energy E-E0 [MeV] rel. energy E-E0 [MeV] 01-101-10-200 200 0-200 200phase@108.4MHz [deg]01rel. particle density01rel. particle densityz=2mcavity inputz=2.55mcavity outputenergy compressionz=2.55mcavity outputphase focusingz=6mtemporal focusf1(Urf)f2(Urf)(a) (b)(c) (d)Figure 2: Simulated longitudinal phase space diagrams forthe two current operation modes when injecting the laseraccelerated proton bunch into the rf cavity at -90 deg syn-chronous phase: energy compression or temporal compres-sion of the bunch along a drift via phase focusing.for phase focusing experiments.Recent results and outlookIn the 2014 campaign, proton bunches with a central energyof 7.8 MeV were selected from the source and propagatedthrough the beamline, containing typically particle num-bers in the range of 2×108 to 5×108 within FWHM. Theirlength could be compressed in time to a FWHM bunchlength of τ=(462±40)ps.The transverse beam profile, however, could be reduced inthe experiment only to a line focus of 3×18 mm2 (FWHM).Therefore, the implementation of a second pulsed solenoidat the end of the beamline is planned as a new steep final fo-cusing system to access highest peak intensities. Also theacceleration of not only protons but also carbon, oxygenand flourine will be explored in 2015.References[1] S. Busold et al., NIMA 740, 94-98 (2014)[2] S. Busold et al., PRSTAB 16, 101302 (2013)[3] S. Busold et al., PRSTAB 17, 031302 (2014)APPA-MML-PP-04 GSI SCIENTIFIC REPORT 2014278 DOI:10.15120/GR-2015-1-APPA-MML-PP-04

Upgrade of GSI's laser-driven ion beamline at Z6

Buch, T.

Scifoni, E.

Durante, M.

Scholz, M.

Friedrich, T.

Modelling dose distributions in cell nuclei after irradiation with ultrasoft X-rays T. Buch1,2, E. Scifoni1, M. Durante1,2, M. Scholz1, and T. Friedrich1 1GSI, Darmstadt, Germany; 2FKP, TU Darmstadt, Germany.The Local Effect Model (LEM) is a mechanistic model to describe cell survival after ion irradiation. Its basic concept is that the biological effect mainly de-pends on the spatial dose distribution within a cell nu-cleus, hereby inducing double-strand breaks (DSB) within DNA substructures called chromatin loops. By means of experimental data, it is known that ul-trasoft X-rays (0.1 – 5 keV) show a higher biological effectiveness than high-energy photons. Similar to high-LET irradiation, this is attributed to a rather inhomogeneous dose distribution due to a considera-bly smaller range of secondary electrons and the high-er significance of attenuation of the photons itself, which results in an increasing yield of DSB. As an extension of LEM for ultrasoft X-rays, this increasing yield can be obtained if the dose distribu-tion of ultrasoft X-rays is known. Employing the track structure simulation program TRAX, which is based on the Monte Carlo method, the dose distribution of ultrasoft X-rays can be examined. Methods The Monte Carlo based program TRAX was developed at GSI to simulate track structures and dose depositions of ion irradiation [1]. Interaction probabilities of various ions with different targets are hereby used for a step-by-step simulation. Since ultrasoft X-rays mainly deposit dose via photoelectric effect [2, 3], the simulation was done using electrons as projectile and water as the cellular target. In a first attempt, the emission of the photoelectrons is assumed to be isotropic and simulations are done for en-ergies between 200 eV and 4.5 keV, with the emphasis on lower energies up to 1.5 keV. To obtain sufficiently pre-cise results, each simulation involved 104 runs. The data obtained by TRAX include the doses for different radii around the emission point of the photoelectron, therefore displaying a spherically symmetric dose distribution D(r). For the analysis of the dose distribution there are two key quantities that need to be examined - the maximum range of the secondary electrons and the center dose at     r = 0. Maximum ranges for different energies were ob-tained by simply taking the last data point on which the dose is not equal to zero. Center doses however were ob-tained by fitting a power line to data points of lower radii and taking the ordinate for r = 0.1 nm, since this repre-sents the minimal radial data given out by TRAX. Results and Discussion The radial dose distributions show similar shapes for all energies. The energy dependence of the maximum range and the center dose are visualized in Fig. 1 and Fig. 2 respectively. It can be seen, that an increasing energy re-sults in an overall more widespread dose distribution, since the increasing range of dose depositions is accom-panied by lower dose depositions in the center.  Figure 1: Maximum range over energy  Figure 2: Center dose over energy As a next step, and hereby presenting a first attempt on the basis of an amorphous track structure, an enhance-ment factor can be computed that describes the increasing yield of DSB for these distribution patterns due to cluster-ing of single strand breaks on the DNA. Because of the overall broader dose distribution of higher energy photo electrons, it is expected to receive a decreasing enhance-ment, and therefore a decreasing biological effectiveness with increasing energy. Comparison with experimental data [2] promises to give an instructive insight into the importance of the inhomogeneity for the biological effec-tiveness of ultrasoft X-rays. Furthermore, since the track ends of ion irradiation also contain low energy photoelec-trons, the results may additionally provide further insight into dose depositions induced by ion irradiation. References [1] Wälzlein C et al., Phys. Med. Biol. 59 1441 (2014) [2] De Lara CM et al., Radiat. Res. 155, 440 (2001) [3] Friedrich T et al., Radiat. Res. 181, 485 (2014)  APPA-HEALTH-04 GSI SCIENTIFIC REPORT 2014294 DOI:10.15120/GR-2015-1-APPA-HEALTH-04

Modelling dose distributions in cell nuclei after irradiation with ultrasoft X-rays

Varentsov, D.

Antonov, O.

Krasik, Y.

Lang, P.

Mariam, F.

Markov, N.

Merrill, F.

Mintsev, V.

Panyushkin, V.

Rodionova, M.

Schanz, M.

Shestov, L.

Bakhmutova, A.

Skachkov, V.

Udrea, S.

Weyrich, K.

Wilde, C.

Zubareva, A.

Bogdanov, A.

Danly, C.

Efimov, S.

Endres, M.

Golubev, A.

Hoffmann, D. H. H.

Kantsyrev, A.

Commissioning of the PRIOR prototype∗D. Varentsov1, O. Antonov2, A. Bakhmutova3, A. Bogdanov3, C.R. Danly4, S. Efimov2, M. Endres5,A.A. Golubev3, D.H.H. Hoffmann5, A. Kantsyrev3, Ya.E. Krasik2, P.M. Lang5, F.G. Mariam4,N. Markov3, F.E. Merrill4, V.B. Mintsev6, V. Panyushkin3, M. Rodionova1,5, M. Schanz5, L. Shestov1,5,V. Skachkov3, S. Udrea5, K. Weyrich1, C. Wilde4, and A. Zubareva61GSI, Darmstadt, Germany; 2Technion, Haifa, Israel; 3ITEP, Moscow, Russia; 4LANL, Los Alamos, USA;5TUD, Darmstadt, Germany; 6IPCP, Chernogolovka, RussiaPRIOR (Proton Microscope for FAIR) is one of thethree frameworks proposed by the HEDgeHOB collabo-ration for the future experiments at FAIR. This world-wide unique high-energy proton microscopy (HEPM) facil-ity will be integrated into the HEDgeHOB SIS-100 beamline and employ high-energy (3 − 10GeV), high-intensity(2.5 · 1013 ppp) proton beams for fascinating multidisci-plinary research such as experiments on fundamental prop-erties of materials in extreme dynamic environments gen-erated by external drivers (pulsed power generators, high-energy lasers, gas guns or explosive-driven generators)prominent for materials research and high energy densityphysics as well as the PaNTERA (Proton Therapy andRadiography) experiment, with a great relevance to bio-physics and medicine.Recently, as a result of the international effort of a teamof scientists from GSI, LANL, ITEP and TUD a PRIORprototype has been designed, constructed and commis-sioned at the HHT area of GSI (Fig. 1 (left)). The PRIORprototype employs high-gradient NdFeB permanent mag-net quadrupole (PMQ) lenses developed by ITEP and pro-vides a magnification of ≈ 4 − 5 with a field of view of≈15mm.Figure 1: The PRIOR prototype PMQ lenses (left) and thepulsed power setup — four high-current generators placedaround a small explosion chamber (right) followed by thefour PRIOR lenses installed at the HHT area of GSI.The detector (image collection) system developed byLANL was installed in the newly constructed concrete-shielded detector room ≈ 9m downstream the target lo-cation. With a pellicle / mirror arrangement, the systememploys two cameras simultaneously: a high resolution(4 Mp) CMOS camera (PCO DIMAX HS) used mainly forstatic experiments and a fast intensified CCD camera (PCODICAM PRO) for dynamic measurements. 10 × 10 cm∗Work supported by GIF grant No. 1132-11.14/2011, BMBF grantsNo. 05K10RD1 and 05P12RDRBK, FRRC contract No. 29-11/13-17 andMES of Russia contract No 14.616.21.0023.columnar CsI and plastic BC-400 scintillators were in-stalled for static and for dynamic measurements, respec-tively.Figure 2: Tantalum step wedge object on a target table(left) and PRIOR proton radiographs (right) of the identi-cal copper and tantalum step wedges (0.56, 2.06, 4.07 and6.05mm step thicknesses).Figure 3: A small women mechanical wrist watch (left)and its proton radiograph (right) obtained with the PRIORprototype using a 3.6 GeV SIS-18 proton beam at GSI.In April 2014, an experimental campaign for the com-missioning of the PRIOR prototype employing 3.5 −4.5GeV, moderate (108−109 ppp) intensity proton beamsfrom the SIS-18 synchrotron took place at GSI. In these ex-periments a large set of small static objects including stepwedges (Fig. 2) and sets of wires made of different met-als, resolution and matching tuning targets as well as somefancy objects (Figs. 3 and 4) were used in a vacuum targetchamber equipped with a 6-axis manipulator. As a result ofthese experiments, an rms spatial resolution of the proto-type of about 30µm with a remarkable density sensitivityhas been demonstrated. It has also been shown that withGSI SCIENTIFIC REPORT 2014 APPA-MML-PP-02DOI:10.15120/GR-2015-1-APPA-MML-PP-02 275Figure 4: A presta valve from a bicycle inner tube (left) anda PRIOR proton radiograph of its central part (right). Onecan clearly see the engagement of the threads as well as thevalve stem and the details of how this valve is seated.a sufficient proton beam intensity (1010 − 1011 ppp) andby using a fast plastic scintillator in the detector system,one can achieve 10 ns or better temporal resolution withoutsignificant degradation of the imaging properties.Figure 5: UEWE water filled target chamber. A thin ex-ploding wire (red) in the center of the chamber is illumi-nated from one side by a proton beam for HEPM measure-ments, and from the other side — by an optical backlighterfor shadowgraphy diagnostics.For the dynamic commissioning of the PRIOR proto-type, a new pulsed power generator had been developed byTechnion and GSI (see Fig. 1 (right)). This generator (upto 50 kV, 12.5 kJ stored energy) was designed to generatewarm dense matter states of various metals by underwa-ter electric wire explosions (UEWE) for equation of statestudies. A metallic wire (30 − 50mm length, 0.1− 1mmdiameter) is placed in the middle of a≈11 cm diameter ex-plosion chamber (Fig. 5). The wire is quickly heated by apulsed electric current (≈200 kA, 1.5− 2µs rise time) to adense plasma conditions with about 2− 3 eV temperature.In addition to the HEPM measurements with the PRIORprototype, an optical shadowgraphy setup consisting of a450-nm, 4-W fiber-coupled laser diode backlighter, twofast intensified CCD cameras and a streak camera has beeninstalled for target diagnostics. A special effort has beentaken to design water shock dumpers in order to minimizethe amount of material used to separate the UEWE explo-sion chamber and the vacuum (10−3mbar) PRIOR beamline as well as the water layer thickness in the proton beamdirection (see Fig. 5).In July 2014, a new experimental campaign aiming com-missioning of the PRIOR prototype for dynamic experi-ments took place at GSI. In comparison with the April2014 run, the proton beam intensity has been increased bymore than two orders of magnitude (up to 1011 protons perpulse) and a new beam diagnostics for high energy protons(scintillator screens and cameras) has been integrated intothe HHT beam line to ensure a good beam alignment andmatching.The dynamic PRIOR experiments have been carriedout using the developed UEWE setup. In these experi-ments, a pulsed current (≈ 40MA/cm2, 5GW depositedpower) run through a tantalum wire (0.8mm diameter and40 − 50mm length) generating this way warm dense mat-ter states characterized by specific energy deposition levelabout 10 kJ/g and∼km/s expansion velocities. An exam-ple of the proton radiography measurements of an explod-ing tantalum wire in shown in Fig. 6. In total, about twelvesuccessful dynamic shots with the PRIOR prototype hasbeen made. In these shots, we have varied the power de-posited in the 0.8mm Ta wires as well as the time momentof the proton radiography imaging. The obtained data iscurrently being processed and analyzed.Figure 6: Proton radiographs (20 ns temporal resolution)of a tantalum wire in water before shot (left) and dur-ing the explosion (right) driven by the UEWE generator(≈ 10 kJ/g specific energy deposition in Ta).As an unexpected result of the commissioning experi-ments, we have observed a considerable image degradationcaused by the radiation damage of the PMQ lenses (thereduction of the quadrupole strength and increased high-order multipole components) due to large fluences of spal-lation neutrons which are mainly produced in the tungstenbeam collimator located in a close proximity to these per-manent magnets. We have also performed special mea-surements and simulations to study this phenomenon. Forthe future applications of the PRIOR magnifier at FAIRwhere much higher proton beam intensities are expectedwe suggest to either consider using the samarium-cobalt(SmCo) PMQ lenses or, better, to design and employ high-gradient small-aperture radiation-resistant warm electro-magnets. The corresponding design study on the finalconstruction of PRIOR for experiments at FAIR has beenstarted.APPA-MML-PP-02 GSI SCIENTIFIC REPORT 2014276 DOI:10.15120/GR-2015-1-APPA-MML-PP-02

Commissioning of the PRIOR prototype