Charge Stripping Research Articles

Development of the carbon foils as charge strippers for high-intensity uranium ion beams

A carbon foil (C-foil) is commonly used as a charge stripper in the heavy-ion accelerators. Since 2005, the polymer-coated carbon foils (PCC-foils) have been fabricated at Nishina Center to prepare larger and thicker C-foils than those previously used as charge strippers. However, the multi-layer PCC-foils did not have sufficiently long life-time. Since August 2009, a new magnetron sputtering system is used to fabricate a thick C-foil. The foils coated with polymer are used as strippers. Life-times of the new single-layer PCC-foils under the uranium beam were measured in two configurations: at the first one a small piece of C-foil was attached to a fixed holder and in the second one a large C-foil was attached to a “rotating-cylinder stripper” device. The properties of the new single-layer PCC-foils and the results of the life-time measurements are reported in this contribution.

Effect of impurities in charge-exchange carbon foil on foil thickness reduction

Carbon thin foils are commonly used as a charge stripping material in particle accelerators. Depending on the original foil thickness, changes in thickness during beam irradiation vary: thin foils (∼10μg/cm2) thicken by build-up, medium thickness foils (∼15μg/cm2) remain unchanged, and thick foils (∼20μg/cm2) become thinner. The thickness reduction differs even under identical manufacturing processes and conditions.The factor causing foil thinning is unknown. On the basis of the low sputtering rate of carbon, it can be said that impurities contained in the foil cause foil thinning.Carbon foils contain impurities such as water. These impurities dissociate and combine with carbon and then evaporate. Taking this into consideration, we examined the gas composition during beam irradiation, to determine which impurity causes foil thinning. As a result, we found that oxygen contained in the foil plays a role in foil thinning.

Charge-state distribution ofU238in nitrogen gas and carbon foil at 14 and15 MeV/nucleon

The charge-state distributions of U with energies of 14 and 15 MeV=nucleon were measured using nitrogen (N2) gas and carbon foil (C-foil) charge strippers. The most probable charge states of U with energies of 14 and 15 MeV=nucleon in N2 gas attain equilibrium at 60.8 and 62.4, whereas those in C-foils attain equilibrium at 75.8 and 76.7, respectively. Novel empirical formulas for the accurate prediction of the equilibrium charge states of U with energies 10–20 MeV=nucleon in gases and C-foil were derived by fitting the data in the energy range of 1–20 MeV=nucleon. The charge states predicted by using the formulas for gases and C-foil are in good agreement with the data in the energy range of 10–20 MeV=nucleon within an average of 0.23 and 0.21, respectively.

Low-Zgas stripper as an alternative to carbon foils for the acceleration of high-power uranium beams

The RIKEN accelerator complex started feeding the next-generation exotic beam facility radioisotope beam factory (RIBF) with heavy-ion beams from 2007 after the successful commissioning of RIBF at the end of 2006. Many improvements made from 2007 to 2010 were instrumental in increasing the intensity of various heavy-ion beams. However, the available beam intensity of very heavy ion beams, especially uranium beams, is far below our goal of $1\text{ }\text{ }\mathrm{p}\ensuremath{\mu}\mathrm{A}$ ($6\ifmmode\times\else\texttimes\fi{}{10}^{12}\text{ }\text{ }\mathrm{particles}/\mathrm{s}$). In order to achieve this goal, upgrade programs are already in progress; the programs include the construction of a new 28-GHz superconducting electron cyclotron resonance ion source and a new injector linac. However, the most serious problem, that of a charge stripper for high-power uranium beams, still remains unsolved, despite extensive research and development work using large foils mounted on a rotating cylinder and a ${\mathrm{N}}_{2}$ gas stripper. A gas stripper is free from problems related to lifetime, though the equilibrium charge state in this stripper is considerably lower than that in a carbon foil, owing to the absence of the density effect. Nevertheless, the merits of gas strippers motivated us to develop a low-$Z$ gas stripper to achieve a higher equilibrium charge state even in gases. We measured the electron-loss and electron-capture cross sections of uranium ions in He gas as a function of their charge state at 11, 14, and $15\text{ }\text{ }\mathrm{MeV}/\mathrm{nucleon}$. The equilibrium charge states extracted from the intersection of the lines of the two cross sections were promisingly higher than those in ${\mathrm{N}}_{2}$ gas by more than 10. Simple simulations of charge development along the stripper thickness were performed by assuming the measured cross sections. The simulation results show that about $1\text{ }\text{ }\mathrm{mg}/{\mathrm{cm}}^{2}$ of He gas should be accumulated to achieve a charge state higher than that of ${\mathrm{N}}_{2}$ gas, notwithstanding the difficulty in accumulation of this helium amount owing to its fast dispersion. However, we now believe that the following two solutions can overcome this difficulty: a gas cell with a very large differential pumping system and a gas cell with a plasma window. Their merits and demerits are discussed in the paper.

Studies of cyclization reactions of linear cumulenes and heterocumulenes using the neutralization–reionization procedure and/or ab initio calculations

A number of linear cumulenes and heterocumulenes have been made by charge stripping of anions of known bond connectivity in the source of a mass spectrometer. Some of these reactive molecules have been identified in interstellar molecular clouds. The structures of these neutrals may be investigated by reionization to a decomposing positive ion [the neutralization-reionization technique ((-)NR(+))], and/or by ab initio calculations. Energized linear cumulenes and heterocumulenes may undergo cyclization to form stable cyclic isomers. To cite a selection of the examples described in this review: (i) four-atom systems CCCC and some heterocumulenes CCCX (X=B, N, Al, Si, P) involve the formation of stable four-membered ring rhombic (also called kite and fan) structures. One of the cyclic molecules, cyclo-C(3) Si, has been detected in interstellar molecular clouds, (ii) five-atom cumulene and heterocumulene systems are more complex. Linear CCCCC rearranges the carbon skeleton by forming a C substituted rhomboid system, CCCCO forms a three-membered cyclic isomer, while nitrogen containing five-atom cumulenes effect nitrile to isonitrile interconversion via three-centered cyclized intermediates, and (iii) CCCCCC and CCCCBO cyclize to give unique six-membered ring systems.

Inhibition of Escherichia coli RNAp by T7 Gp2 Protein: Role of Negatively Charged Strip of Amino Acid Residues in Gp2

Gp2, a 7 kDa protein encoded by T7 bacteriophage, is a potent inhibitor of Escherichia coli RNA polymerase (RNAp), the enzyme responsible for transcription of all bacterial genes and early viral genes. A prominent feature in the structure of Gp2 is a contiguous strip of seven negatively charged amino acid residues (negatively charged strip or NCS), located along one side of the molecule. The role of the NCS in Gp2 function is not known. Here, the in vivo and in vitro properties of altered forms of Gp2 with amino acid substitutions in the NCS are described. While mutations in the NCS do not compromise the folding or the ability of Gp2 to bind to the RNAp β′ subunit, disruption of the NCS significantly attenuates Gp2 function in vivo and its ability to inhibit RNAp in vitro. Efficient inhibition of the RNAp by Gp2 also involves the amino terminal region 1 domain of the RNAp promoter specificity subunit σ 70, located in the vicinity of the primary Gp2 binding site in β′. The results are discussed in the context of hypothetical molecular mechanisms of RNAp inhibition by Gp2.

Evolution of low‐altitude and ring current ENA emissions from a moderate magnetospheric storm: Continuous and simultaneous TWINS observations

The moderate storm of 22 July 2009 is the largest measured during the extended solar minimum between December 2006 and March 2010. We present observations of this storm made by the two wide‐angle imaging neutral‐atom spectrometers (TWINS) mission. The TWINS mission measures energetic neutral atoms (ENAs) using sensors mounted on two separate spacecrafts. Because the two spacecrafts' orbital planes are significantly offset, the pair provides a nearly optimal combination of continuous magnetospheric observations from at least one of the TWINS platforms with several hours of simultaneous, dual‐platform viewing over each orbit. The ENA imaging study presented in this paper is the first reported magnetospheric storm for which both continuous coverage and stereoscopic imaging were available. Two populations of ENAs are observed during this storm. The first are emissions from the ring current and come from a parent population of trapped ions in the inner magnetosphere. The second, low‐altitude emissions (LAEs), are the result of precipitating ions which undergo multiple charge exchange and stripping collisions with the oxygen exosphere. The temporal evolution of this storm shows that the LAEs begin earlier and are the brightest emissions seen during the main phase, while later, during the recovery, the LAE is only as bright as the bulk ring current emissions.

Charge-state distribution measurements ofU238andXe136at11 MeV/nucleonusing gas charge stripper

The charge-state distributions and equilibrium charge states of uranium ($^{238}\mathrm{U}$) and xenon ($^{136}\mathrm{Xe}$) ions at $11\text{ }\text{ }\mathrm{MeV}/\mathrm{nucleon}$ were determined using a gas charge stripper. A differential pumping system facilitated the increase of the nitrogen gas thickness up to $1.3\text{ }\text{ }\mathrm{mg}/{\mathrm{cm}}^{2}$, which is sufficient for the most probable charge state to attain equilibrium. The charge states of $^{238}\mathrm{U}$ attain equilibrium at 56.0, 56.6, and 55.7 in ${\mathrm{N}}_{2}$, Ar, and ${\mathrm{CO}}_{2}$ media with thicknesses of 125, 79, and $126\text{ }\text{ }\ensuremath{\mu}\mathrm{g}/{\mathrm{cm}}^{2}$, respectively, while those of $^{136}\mathrm{Xe}$ attain equilibrium at 40.5, 40.1, and 40.3 in ${\mathrm{N}}_{2}$, Ar, and ${\mathrm{CO}}_{2}$ media with thicknesses of 163, 95, and $139\text{ }\text{ }\ensuremath{\mu}\mathrm{g}/{\mathrm{cm}}^{2}$, respectively. The equilibrium charge states of $^{136}\mathrm{Xe}$ are acceptable for acceleration by the subsequent cyclotron. The measured data of $^{238}\mathrm{U}$ were used to devise an empirical formula for the prediction of the equilibrium charge state in gaseous media over the energy region of $0.01--60\text{ }\text{ }\mathrm{MeV}/\mathrm{nucleon}$. The equilibrium charge state of $^{136}\mathrm{Xe}$ as predicted by the devised formula is in good agreement with the data.

How Does Energized NCCCCCN Lose Carbon in the Gas Phase? A Joint Experimental and Theoretical Study

Neutral NCCCCCN may be prepared in a collision cell of a VG ZAB 2HF mass spectrometer by charge stripping of (NCCCCCN)(*-), formed in the ion source by the process NCCCCH(OEt)(CN) + HO(-) --> H(2)O + NCCCC(-)(OEt)(CN) --> (NCCCCCN)(*-) + EtO(*). A comparison of the neutralization/reionization ((-)NR(+)) and charge reversal ((-)CR(+)) spectra of (NCCCCCN)(*-) indicate that some neutrals NCCCCCN are energized and rearrange to an isomer which decomposes by loss of carbon. An ab initio study at the CCSD(T)/cc-pVTZ//B3LYP/6-311+G(3df) level of theory indicates that (i) triplet NCCCCCN is the ground state with a T/S energy gap of -14.9 kcal mol(-1); (ii) the structures of triplet and singlet NCCCCCN need to be described by molecular obital theory, and a simple valence bond approach cannot be used for this system; and (iii) there are several possible routes by which an energized neutral may lose carbon, but the major route involves the triplet nitrile to isonitrile rearrangement NCCCCCN --> CNCCCCN --> NCCCCN + C.

Charge strippers for high intensity uranium beams in the RIKEN RI beam factory

We have developed carbon stripper foils, liquid Li strippers, and gas strippers to find the most suitable stripper for high intensity uranium ion beams at the RIKEN RI beam factory (RIBF). The lifetime of newly developed polymer coated carbon foils has been measured online with a beam. A water stripper has been developed offline as a test for a liquid lithium stripper. A windowless gas target has been used as a nitrogen gas stripper and tested offline with the gas injected into the target cell. The maximum pressure of the target cell was 9.25 kPa, which corresponds to a thickness of 1.04 mg/cm 2.

Development of long-life carbon stripper foils for uranium ion beams

Carbon foils (C-foils) are extensively used as charge strippers for heavy-ion beams at the RIKEN RI beam factory. Multi-layer polymer coated C-foils (PCC-foils) of 300 μg/cm 2 carbon thickness were irradiated by a 11 MeV/nucleon 238U 35+ beam and their lifetimes were measured. Using an atomic force microscope (AFM) and an electron probe microanalyzer (EPMA), it was observed that the surface property and cross-sectional image of the PCC-foils had changed after the irradiation. A rotating-cylinder stripper device, which was developed to further increase the lifetime of C-foils, was also tested.

Two small thermodynamically stable organic dications

Small multiply charged species may be long-lived without the benefit of stabilization by a medium, primarily owing to the Coulomb barrier that impedes both formation and dissociation of the systems. We extend the category of small organic dicationic structures that may possess thermodynamic stability to include derivatives of cyanoacetylene. The linear dication HCCCNH(2+) and its isomer HCCNCH(+2) are characterized in detail; according to CCSD(T)/6-31G(d,p)//MCSCF(7,13)/6-31G(d,p) estimates, HCCCNH(2+) is thermodynamically stable by 2.8 eV and the barrier to colinear dissociation is ca 4.1 eV. The isomer HCCNCH(2+) is thermodynamically stable by about 2.1 eV and the barrier to colinear dissociation is ca 4.5 eV. Preparation of these systems by charge stripping of the predecessor H 2C 3N monocation may be feasible.

Research Highlights

Research Highlights

Development of a liquid lithium thin film for use as a heavy ion beam stripper

A series of experiments was performed to investigate the feasibility of a liquid lithium thin film for a charge stripper in a high-power heavy ion linac. Various preliminary experiments using simulants were first conducted to determine the film formation scheme, to investigate the film stability, and to obtain the design parameters for a liquid lithium thin film system. Based on the results from these preliminary studies, a prototypical, high pressure liquid lithium system was constructed to demonstrate liquid lithium thin film formation. This system was capable of driving liquid lithium at ≲300 °C and up to 13.9 MPa (2000 psig) through a nozzle opening as large as 1 mm (40 mil) in diameter. This drive pressure corresponds to a Li velocity of >200 m/s. A thin lithium film of 9 mm in width at velocity of ∼58 m/s was produced. Its thickness was estimated to be roughly ≲13 μm. High vacuum was maintained in the area of the film. This type of liquid metal thin film may also be used in other high power beam applications such as for intense X-ray or neutron sources.

Anions [N(CH2)3]− and [ON(CH2)2]− are Stable in the Gas Phase, but Can They Be Charge Stripped to Form the Radicals N(CH2)3 and ON(CH2)2? A Joint Experimental and Theoretical Study

Collision-induced activation of deprotonated trimethylamine N-oxide yields the two anions [N(CH(2))(3)](-) and [ON(CH(2))(2)](-) following losses of H(2)O and CH(4), respectively. These two anions decompose by minor losses of H(*) and H(2) when collisionally activated: no other fragmentations are noted. Calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31+G(d) level of theory indicate that these trigonal anions are stable, and should not rearrange following collisional activation. Collisional-induced charge stripping of the anions [N(CH(2))(3)](-) and [ON(CH(2))(2)](-), respectively, form N(CH(2))(3) and ON(CH(2))(2). Some of these neutrals are energised and undergo rearrangement and dissociation. From a consideration of experiment and theory, it is proposed (i) that energised N(CH(2))(3) may cyclise to form the 1-aziridinylcarbinyl radical. This species may ring open to CH(2)=NCH(2)CH(2) which then decomposes to CH(2)N and C(2)H(4) and (ii) energised ON(CH(2))(2) may undergo OC cyclisation followed by ring opening to energised CH(2)=NCH(2)O which may fragment to yield CH(2)N and CH(2)O.

Nonuniform Electro-osmotic Flow on Charged Strips and Its Use in Particle Trapping

In this article, we investigate theoretically electro-osmotic flow set up by charged strips on an otherwise uncharged surface. Starting with a single-strip problem we demonstrate that for simple polynomial surface charge distributions several basic solutions can be derived in closed forms constituted by the analogous idea-flow solutions, which provide a more lucid way of revealing the flow features. These solutions reveal two types of flow topology: simple draining-in/pumping-out streaming and a pair of microvortices for symmetric and antisymmetric surface charge distributions, respectively. For an arbitrary surface charge distribution, more complicated flow structures can be found by the superposition of these basic solutions. We further extend the analysis to two uniformly charged strips and show how the flow characteristics vary with the strips' dimensions and surface zeta potentials. The far-field velocity behavior is also asymptotically identified and indicates that the hydrodynamic nature of the flow is typically long-range. An application to particle trapping with electro-osmotic vortices is also investigated theoretically for the first time. We show that in collaboration with short-range attraction effects the trapping can be facilitated by symmetric vortices with a converging stagnation point, but not by asymmetric vortices.

The lower exosphere of Titan: Energetic neutral atoms absorption and imaging

The Saturn magnetosphere interacts with the Titan atmosphere through various mechanisms. One of them leads, by charge exchange reactions between the energetic Saturnian ions and the exospheric neutrals of Titan, to the production of energetic neutral atoms (ENAs). The Ion and Neutral Camera (INCA), one of the three sensors that comprise the Magnetosphere Imaging Instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images the ENA emissions in the Saturnian magnetosphere. This study focuses on the ENA imaging of Titan (for 20–50 keV H ENAs), with the example of the Ta Titan flyby (26 October 2004): our objective is to understand the positioning of the ENA halo observed around Titan. Thus we investigate the main ENA loss mechanisms, such as the finite gyroradii effects for the parent ions, or the charge stripping with exospheric neutrals. We show that multiple stripping and charge exchange reactions have to be taken into account to understand the ENA dynamics. The use of an analytical approach, taking into account these reactions, combined with a reprocessing of the INCA data, allows us to reproduce the ENA images of the Ta flyby and indicates a lower limit for ENA emission around the exobase. However, the dynamics of energetic particles through the Titan atmosphere remains complex, with an inconsistency between the ENA imaging at low and high altitudes.

Charge stripping accumulation of light heavy ions in HIRFL-CSR main ring**Supported by National Scientific Project HIRFL-CSR

The charge stripping injection method has been adopted for the accumulation of light heavy ions in HIRFL-CSR. This method has some special requirements for the accelerating particles, and at the same time the structure of the injection orbit has to be changed. In this paper, the design of the orbit has been presented, as well as the calculation of the beam line matching. According to the result of commissioning, stripping injection can accumulate the beam to a higher current.

Field Measurement of DC Magnets at 3-GeV RCS in J-PARC

The J-PARC RCS (rapid cycling synchrotron) is designed to inject the beam from the LINAC, to change their charge from to , to accelerate the beam from 400 MeV to 3 GeV, with protons per pulse at 25 Hz repetition rate, and to extract the beam after the acceleration to the MLF (material and life science experimental facility) and the MR (main ring). Thus the RCS has the beam circulating ring and three beam transport lines. The RCS ring consists of several magnets, and the DC magnets are installed for beam injection and extraction. The four steering magnets and two septum magnets are installed at injection line in order to adjust the beam injection point. One quadratic magnet, two steering magnet and two septum magnets are installed at dump line for the part of the beam with their charge not changed from to at the charge stripping foil. Two deflecting magnets to kick out the beam without exciting the pulse kicker magnets and three septum magnets are installed at the extraction line. Up to now, the DC magnets are developed and manufactured, the field measurements are carried out, and magnets installation into the RCS tunnel are finished. The field distributions of DC magnets are measured by using the new field mapping system with three one-dimensional hall-probes on a 3-axis movable stage. In the case of the quadrupole magnet, the field measurements are not only field mapping but also analyze its magnetic higher order components by the harmonic rotating coil. As a result, the measured field quality meets the design performance requirements of the DC magnets.

Gas-Phase Proton-Transfer Chemistry Coupled with TOF Mass Spectrometry and Ion Mobility-MS for the Facile Analysis of Poly(ethylene glycols) and PEGylated Polypeptide Conjugates

Gas-phase ion/molecule chemistry has been combined with ion mobility separation and time-of-flight mass spectrometry to enable the characterization of large poly(ethylene glycol)s (PEGs) and PEGylated molecules (>40 kDa). A facile method is presented in which gas-phase superbases are reacted in the high-pressure source region of commercial TOF mass spectrometers to manipulate the charge states of large ions generated by electrospray ionization (ESI). Charge stripping decreases the spectral congestion typically observed in ESI mass spectra of high molecular weight polydisperse PEGylated molecules. From these data, accurate average molecular weights and molecular weight distributions for synthetic polymers and PEGylated proteins are determined. The average MW measured for PEGylated Granulocyte colony-stimulating factor (rh-GCSF, 40 726.2 Da) is in good agreement with the theoretical value, and a 16 Da mass shift is easily observed in the spectrum of an oxidized form of the heterogeneous PEGylated protein. Ion mobility separations can fractionate PEGs of different chain length; when coupled with charge stripping ion/molecule reactions, ion mobility mass spectrometry (IMMS) offers several analytical advantages over mass spectrometry alone for the characterization of large PEGylated molecules including enhanced dynamic range, increased sensitivity, and specificity. Low abundance free PEG in a PEGylated peptide preparation, which is not directly detectable by mass spectrometry, can be easily observed and accurately quantified with gas-phase ion/molecule chemistry combined with ion mobility mass spectrometry.