Determination of Hydrogen Density by Swift Heavy Ions

Abstract

A novel method to determine the total hydrogen density and, accordingly, a precise plasma temperature in a lowly ionized hydrogen plasma is described. The key to the method is to analyze the energy loss of swift heavy ions interacting with the respective bound and free electrons of the plasma. A slowly developing and lowly ionized hydrogen theta-pinch plasma is prepared. A Boltzmann plot of the hydrogen Balmer series and the Stark broadening of the H_{β} line preliminarily defines the plasma with a free electron density of (1.9±0.1)×10^{16} cm^{-3} and a free electron temperature of 0.8-1.3 eV. The temperature uncertainty results in a wide hydrogen density, ranging from 2.3×10^{16} to 7.8×10^{18} cm^{-3}. A 108 MHz pulsed beam of ^{48}Ca^{10+} with a velocity of 3.652 MeV/u is used as a probe to measure the total energy loss of the beam ions. Subtracting the calculated energy loss due to free electrons, the energy loss due to bound electrons is obtained, which linearly depends on the bound electron density. The total hydrogen density is thus determined as (1.9±0.7)×10^{17} cm^{-3}, and the free electron temperature can be precisely derived as 1.01±0.04 eV. This method should prove useful in many studies, e.g., inertial confinement fusion or warm dense matter.

Energy loss of Fe ions in He plasmas at different thermodynamic states

“…The differences in the average ionization and the ion abundances obtained from the different atomic kinetics models for some ranges of plasma conditions will influence the theoretical calculations of the projectile energy loss in the plasma, Eqs. ( 6) and (7). To analyze this, we have studied the influence of the atomic kinetics model in the calculation of the total stopping number, L…”

“…The understanding of the interactions of swift charged particles with plasmas is fundamental to determine the energy deposition of the beam inside the plasma. [4][5][6][7] Therefore, a full theoretical method is needed to calculate correctly this energy deposition of projectile ions in any kind of laboratory plasmas. The energy loss of ions in local thermal equilibrium (LTE) plasmas has been widely studied.…”

Contrasting ion stopping models at medium energies in partially ionized plasmas

“…Ion stopping power in high density plasmas plays a crucial role in the development of inertial confinement fusion (ICF), and an accurate description of the ion energy deposition in the ignition and combustion phases of the deuterium-tritium fuel is very important. The energy deposition of ions in high density plasmas is currently investigated with special interest in low and medium energy projectiles [5,6], i.e. in the energy range where a higher stopping power appears.…”

Diagnosis of bound electron density by measuring energy loss of proton beam in partially ionized plasma target

“…Zhang等 [9] 利用光纤干涉方法诊断了紧凑环中的 He等离子体的自由电子密度; 然而, 上述光学类诊 断技术仅针对等离子体中的自由电子成分, 瞬态光 谱仅能反应自由电子信息; 汤姆孙散射方法中的散 射过程主要来自自由电子, 以及束缚电子密度对等 离子体折射率的贡献很小, 现有的激光干涉法等均 无法诊断部分电离等离子体中束缚电子密度信息 [7][8][9] . Xu等 [10] 利用德国GSI的UNILAC束线提供 的3.65 MeV/u 48 Ca 10+ 离子束与角箍缩放电形式 产生的氢等离子体靶作用, 实验测量了出射离子电 荷态分布与离子的能损; 结合角箍缩等离子体特征 光谱诊断结果, 分析了H β 线的Stark展宽, 取得 了该等离子体的电子温度与自由电子密度等信息, 最后利用Bethe公式对重离子束在等离子体中的 能损进行计算, 考虑到该等离子体靶空间的高均匀 性以及在该能区下的离子的阻止本领数值基本不 变, 因此离子能损函数可简化为 [11] ∆E ∝ Z 2 eff [( dE dx 究工作, 取得大量的可靠数据 [11] .…”