Space-charge effects in the catcher gas cell of a rf ion guide

Takamine, A.; Wada, M.; Ishida, Yoshihisa; Nakamura, Takashi; Okada, Kazuya; Yamazaki, Y.; Kambara, T.; Kanai, Y.; Kojima, Takao; Nakai, Y.; Oshima, Nobuyuki; Yoshida, Akihiro; Kubo, T.; Ohtani, S.; Noda, K.; Katayama, Ichiro; Hostain, P.; Varentsov, V.; Wöllnik, H.

doi:10.1063/1.2090290

Cited by 67 publications

(53 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(1)) by increasing or by building the RF-carpet with a reduced √2 0 separation between neighboring electrodes [8]. So far RF-carpets have mainly been used to concentrate energetic heavy-ion reaction products for further analyses [5,6,8]. This was achieved in large gas-filled vessels that contain RF-carpets (see Figure 4).…”

Section: Figurementioning

confidence: 99%

“…If additional electric fields are formed between neighboring electrodes, the hovering ions can be moved to an extraction orifice located at the center of the RF-carpet by DC-fields [6] or by fields of a travelling wave [7]. Consequently to the n th carpet electrode one of the following potentials should be applied:…”

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

“…For singly charged ions the ion repelling force of the RF-carpet can be calculated [5,6] for every distance above the RF-carpet by assuming that two neighboring electrodes are the electrodes of a quadrupole of aperture 2 0 between which a potential difference exists. The magnitude of this force is found as:…”

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

“…A big improvement over the use of wire electrodes as shown in Figure 1 was to use N concentric ring electrodes formed as a conical or planar printed circuit board, a so-called RF-carpet [5,6] shown in Figure 2. Also in this electrode configuration high frequency fields are established between neighboring electrodes to which potentials = ± 00 cos 00 are applied, which cause the ions to be repelled from the surface of the RF-carpet and to hover above it, wherein 00 was several MHz.…”

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

“…In the case of Eq. (2) separate potentials must be provided to each ring electrode [5,6]. In the case of Eq.…”

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

See 4 more Smart Citations

RF-Carpets that Compress Ions to High Density Beams

Wöllnik

Arai²,

Ito³

et al. 2015

Microsc Microanal

Self Cite

View full text Add to dashboard Cite

Ions that are moved by electric fields in gases follow quite exactly the electric field lines since these ions have substantially lost their kinetic energies in collisions with gas atoms or molecules and so carry no momenta. Shaping the electric fields appropriately the phase space such ion beams occupy can be reduced and correspondingly the ion density of beams be increased. IntroductionIon clouds can be shaped by electric fields only in so far as is allowed by Liouville's theorem [1], which states that the magnitude of the phase space occupied by an ion beam, which moves in vacuum, can not be changed. Ion beams that move in gases do not have this limitation, since they move substantially along electric field lines between collisions with gas atoms or molecules. However, ion clouds that move in gases increase their volumes over time by diffusion, so that the clouds' lateral and longitudinal dimensions increase with the square root of time. Consequently, ion beams cannot easily be focused to fine points, but wide ion beams can be transformed to narrow ones with increased ion densities.

show abstract

Section: Figurementioning

confidence: 99%

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

“…In the case of Eq. (2) separate potentials must be provided to each ring electrode [5,6]. In the case of Eq.…”

Section: Compression Of Clouds Of Slowed Down High-energy Ionsmentioning

confidence: 99%

See 3 more Smart Citations

RF-Carpets that Compress Ions to High Density Beams

Wöllnik

Arai²,

Ito³

et al. 2015

Microsc Microanal

Self Cite

View full text Add to dashboard Cite

show abstract

The cyclotron gas stopper project at the NSCL

et al. 2007

Self Cite

View full text Add to dashboard Cite

Gas stopping is becoming the method of choice for converting beams of rare isotopes obtained via projectile fragmentation and in-flight separation into low-energy beams. These beams allow ISOL-type experiments, such as mass measurements with traps or laser spectroscopy, to be performed with projectile fragmentation products. Current gas stopper systems for high-energy beams are based on linear gas cells filled with 0.1-1 bar of helium. While already used successfully for experiments, it was found that space charge effects induced by the ionization of the helium atoms during the stopping process pose a limit on the maximum beam rate that can be used. Furthermore, the extraction time of stopped ions from these devices can exceed 100 ms causing substantial decay losses for very short-lived isotopes. To avoid these limitations, a new type of gas stopper is being developed at the NSCL/MSU. The new system is based on a cyclotron-type magnet with a stopping chamber filled with Helium buffer gas at low pressure. RF-guiding techniques are used to extract the ions. The space charge effects are considerably reduced by the large volume and due to a separation between the stopping region and the region of highest ionization. Cyclotron gas stopper systems of different sizes and with different magnetic field strengths and field shapes are presently investigated.

show abstract