Mirror Cell Research Articles

Stabilization of an axisymmetric tandem mirror cell by a hot plasma component

A hot plasma component formalism is used for a symmetric tandem mirror cell to relate the precessional mode, well known from Astron experiments, to more standard magnetohydrodynamic (MHD) modes. The l=1 mode can be stabilized by conducting walls, while the higher l modes can be stabilized by finite Larmor radius. Such a configuration is free of remnant dissipative instabilities because all perturbations are positive energy excitations when stability is achieved. OFF

Modification of the macroscopic stability of a tandem mirror by partial line-tying

Increased stability is observed during experiments with gun injection in the Phaedrus tandem mirror. This is manifested by three effects. First, a magnetic mirror cell with bad average curvature, adjacent to a plasma gun, confines plasma with betas up to 20%. Second, the central cell, also with bad curvature, is stable at betas up to 20%, exceeding the minimum-B interchange stability limit by a factor of 20. Third, the quadrupole magnetic field required for interchange stability is reduced. These effects are shown to agree with a theory of line-tying stabilization, supplemented by minimum-B stabilization.

Alfvén ion-cyclotron instability in tandem-mirror plasmas. II

The linear theory of Alfvén ion-cyclotron instability is extended by a rigorous treatment of plasma nonuniformity along the equilibrium magnetic field. A standard phase-integral dispersion relation provides stability boundaries. Two ion distribution functions allow modeling of plasmas formed in various ways, including neutral-beam injection both perpendicular and oblique to magnetic field lines. Stability results are quantitatively consistent with past and present experiments. The results further indicate that two important features of stable mirror cells in future experiments are large mirror ratios and pitch-angle distributions that are broad or are peaked far from perpendicular to the magnetic field.

Alfvén ion-cyclotron instability in tandem-mirror plasmas. I

The linear theory of Alfvén ion-cyclotron instability is studied for ion distributions that model those in tandem-mirror plasmas. The uniform-plasma approximation leads to the following qualitative stability results. Distributions that fill a mirror cell of mirror ratio R have stability limits for beta (plasma pressure/magnetic-field pressure) that increase rapidly with R. Warm ions can damp instability caused by anisotropic hot ions. Injection of neutral beams at angles far from perpendicular to the magnetic field is a method of plasma formation with good stability properties. A plasma composed of ions with different charge-to-mass ratios can achieve beta approximately twice as large as for a single-ion-species plasma. The model distributions used here are convenient also for the eikonal treatment of axially nonuniform plasmas, which are studied in a subsequent paper.

Ballooning instabilities in hot electron plasmas

The stability of short-wavelength, low-frequency modes in a hot electron plasma is investigated. Particular attention is devoted to the effect of the dependence of perturbed quantities along the equilibrium magnetic field lines. Two types of modes in a bumpy torus are considered: modes which are nearly flutes in each mirror cell but vary in phase from cell to cell, and modes which have significant variation in each cell. Generally speaking, allowing perturbations to vary along the field lines is destabilizing. However, sufficiently large hot electron gyroradii can stabilize all short perpendicular wavelength modes.

Rf Stabilization of an Axisymmetric Tandem Mirror

Plasma with significant central-cell beta can be sustained in a tandem mirror composed of three axisymmetric simple mirror cells by the use of ion-cyclotron resonant heating. Radial ponderomotive force due to the rf electric field opposes the centrifugal force due to the field-line curvature to ensure interchange stability. This is indicated by the sensitive dependence of the plasma stability on the sign of the difference between the rf frequency and the ion-cyclotron frequency.

Pulse shortening in dye laser side-pumped by TEA N<inf>2</inf>laser

The temporal behavior of the output from a homemade TEA-N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -laser (750 ps pulsewidth) pumped dye (R6G) laser was observed with the aid of a streak camera. The observed output pulsewidths are between 60 and 160 ps depending on the configuration of the dye laser cavity. The shortest (50 ps) pulse is obtained when the distances between output mirror and dye cell, and dye cell and grating, are 10 and 105 mm, respectively. The mechanism of the short pulse generation is clarified by comparing experimental results with the results obtained by solving rate equations numerically, where the position dependences of excited-state population and photon flux were taken into account.

Unfavorable prognostic significance of hand mirror cells in childhood acute lymphoblastic leukemia. A report from the childrens Cancer Study Group.

The prognostic significance of hand mirror cells (HMCs) in childhood acute lymphoblastic leukemia was determined by quantifying the percentage of these cells in the diagnostic bone marrow aspirates of previously untreated children entered on the Childrens Cancer Study Group protocol 141. Of 664 examinable patients, 39 (5.9%) had greater than 10% HMCs, and only four (0.6%) had greater than 30% HMCs. Compared with the entire study population, a greater proportion of children with more than 10% HMCs were older than 10 years of age, had hemoglobin levels greater than 10 g/dL, and had undifferentiated lymphoblast morphology. The children with more than 10% HMCs had a higher rate of bone marrow relapse, poorer disease-free survival, and shorter survival than patients with less than 10% HMCs. By multivariate analysis, HMC morphology was an independent, unfavorable prognostic factor.

A Preshaping Transition Coil for a Small Minimum-B Magnetic Mirror

An additional coil between the plasma source and the mirror cell prefans incoming plasma to map it directly into the well-known twisted bow-tie shape and thus avoids reshaping drifts generated in conventional min-B mirror machines. This reduces vacuum chamber size requirements and eliminates any drift reshaping delay. Wound in series with the standard quadrupole loffe bar set, this dual-coil system features end connections which contribute no field on axis.

Strongly-localized ballooning modes in an axisymmetric tandem mirror

A simple model of an axisymmetric tandem mirror without thermal barriers is employed to study the stability of ballooning modes which are confined to the central mirror cell. The central cell is treated as long-thin with isotropic pressure, while the end plug is modeled by a line-tying boundary condition. The scaling of βc with the mirror ratio R* and the connection length Lc is computed, and the sensitivity of these results to the magnetic field profile chosen is discussed.

Viscous plasma flow in a multiple-mirror configuration

The steady-state, axial plasma confinement by a multiple-mirror device is studied in the ’’viscous fluid regime,’’ λ/lm≪1 (but not negligible), where λ is the ion-ion mean-free-path and lm is the scale length of magnetic field variations. An approximate analytical solution is obtained by averaging over the rapid variations caused by the individual mirrors and compared to a numerical solution without averaging. A smooth transition is found, with increasing values of λ/lm, from sonic flow to a diffusive flow. Studies are made of the variation in density profiles and confinement times versus λ/lm, mirror ratio, relative mirror width, and number of mirror cells. The viscous fluid regime is found to have the same characteristics as the ideal multiple-mirror regime for λ/lm→1.

Studies of an Unneutral Electron Cloud in the CFIA

In the Collective Focusing Ion Accelerator (CFIA) scheme, a non-neutral electron cloud is trapped in a multiple mirror toroidal magnetic field. The electrons' radial electrostatic field serves to confine and focus an accelerated ion beam. The ion beam, with a density up to 10% that of the electrons', is accelerated by an induced toroidal electric field. The induced toroidal electric field, however, is not strong enough to overcome the mirror force acting on the electrons. This scheme enables the construction of a very small radius accelerator in the GeV range. As a first stage in the development of the CFIA, it is necessary to demonstrate trapping and stability of a non-neutral electron cloud over a long time (a few msec). It is also necessary to show that the electron cloud remains confined to the mirror cells when an accelerating toroidal electric field is applied. 5 refs.

Particle confinement in asymmetric-cell multiple-mirror systems

The enhancing effect of asymmetry in the particle capture and loss processes in a multiple-mirror system is analysed. The system considered consists of a central mirror confinement region ‘plugged’ at each end by N smaller-volume mirror cells. It is shown that the effective confinement time in the central cell increases exponentially with N with asymmetric cells, as contrasted with previous analyses which showed an increase linear in N for plugging cells characterized by symmetric capture and loss processes.

Antigen-Antibody Complexes Related to the Baboon Endogenous Virus in Humans With Acute Lymphoblastic Leukemia-Hand Mirror Variant (ALL-HMC)

AbstractHand mirror cells are a morphological configuration that are seen in immunologically stimulated lymphocytes and can be induced by antigen-antibody complexes. Therefore, the bone marrow and peripheral blood plasma of two patients with acute lymphoblastic leukemia-hand mirror variant were evaluated for the presence of antigen-antibody complexes. Both patients had antigen-antibody complexes in the bone marrow plasma and not in the peripheral blood plasma as determined by double counter-current immunoelectrophoresis. The antigen moiety of these complexes appears immunologically related to components of the baboon endogenous virus (BaEV), and the antibody moiety also appears related to structural components of the BaEV. Bone marrow plasmas from patients without leukemia were evaluated for the presence of antigen-antibody complexes and found to be negative. The antigen-antibody complexes may account for the presence of hand mirror cells in the bone marrow of patients with acute lymphoblastic leukemia-hand mirror variant.

Antigen--antibody complexes related to the baboon endogenous virus in humans with acute lymphoblastic leukemia--hand mirror variant (ALL-HMC)

Hand mirror cells are a morphological configuration that are seen in immunologically stimulated lymphocytes and can be induced by antigen-- antibody complexes. Therefore, the bone marrow and peripheral blood plasma of two patients with acute lymphoblastic leukemia--hand mirror variant were evaluated for the presence of antigen--antibody complexes. Both patients had antigen--antibody complexes in the bone marrow plasma and not in the peripheral blood plasma as determined by double counter- current immunoelectrophoresis. The antigen moiety of these complexes appears immunologically related to components of the baboon endogenous virus (BaEV), and the antibody moiety also appears related to structural components of the BaEV. Bone marrow plasmas from patients without leukemia were evaluated for the presence of antigen--antibody complexes and found to be negative. The antigen--antibody complexes may account for the presence of hand mirror cells in the bone marrow of patients with acute lymphoblastic leukemia--hand mirror variant.

Infectious mononucleosis and acute lymphoblastic leukemia—hand mirror cells: A qualitative and quantitative ultrastructural study

The hand mirror cell (HMC) in infectious mononucleosis (IM) is a T cell which appears at the time of improvement and apparently has an important role in immune surveillance. Fifty electron micrographs of HMC from an unusual untreated patient with ALL-HMC variant were compared to 50 electron micrographs of HMC from five patients beginning to recover from IM. Quantitative differences between the IM-HMC and ALL-HMC were observed in multivariate analysis of variance (p < 0.001), nuclear perimeter (p < 0.0001), nuclear length (p < 0.0001), cytoplasmic length (p < 0.0001), total cell area (p < 0.0001), cytoplasmic area (p < 0.0001) and nuclear cytoplasmic ratio (p < 0.004), and numbers of mitochondria (p < 0.001). The qualitative differences included greater nuclear irregularity in the IM-HMC, and prominent nucleolonema in some of the ALL-HMC. In addition, the IM-HMC showed more polyribosomes, parallel tubular arrays and microtubules, but much less glycogen. Since the IM-HMC apparently enter effectively into immune surveillance, and some cases of ALL have HMC, the ultrastructural similarities and differences above contribute to a better understanding of the importance of this unique cell configuration in benign and malignant disorders.

High density plasma confinement in a multiple mirror

Improved plasma confinement is observed in a multiple mirror magnetic field configuration, where the plasma density is so high that the ion mean free path is much shorter than the mirror cell length.

Axisymmetric sloshing-ion tandem-mirror plugs

By injecting neutral beams close to the loss cone of a deep, axisymmetric mirror cell and locally heating electrons, an ambipolar potential can be established having a minimum at the midplane and a strong off-midplane peak on one side of the midplane. Such a mirror cell could serve as a plug for a tandem-mirror machine, thus eliminating the problems associated with non-axisymmetry of ion orbits. A minimum-B cell located outside this axisymmetric cell could then be added as an MHD anchor.

Injection and containment of an unneutralized electron cloud in a bumpy toroidal magnetic field

We report on the successful injection, compression, and confinement of an unneutralized electron cloud in a multiple-mirrored toroidal magnetic field geometry. About 2×1012 electrons were compressed to maximum energy of 500 keV. The lifetime of the cloud was limited by the decaying magnetic field. During its lifetime, the cloud was found to perform m=1 diocotron oscillations. Two injectors were operated in two separate mirror cells, and their mutual interaction was studied.

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A Moloney murine leukemia virus-induced T-cell preleukemic thymic lymphoma tissue culture from an inbred C3H/HeJ mouse contained numerous hand mirror cells (HMC). The cells were studied by light and phase-contrast microscopy, special stains, indirect immunofluorescence for terminal deoxynucleotidyl transferase, and scanning and transmission electron microscopy. The uropods of the mouse and human HMC were similar. In contrast, viruses were noted on the tip of the mouse HMC uropod by transmission electron microscopy. These observations, reported for the first time in an animal model, will enable investigators to study the HMC under controlled conditions.