To date, a variety of different types of mass spectrometers have been utilized on missions to study the composition of atmospheres of solar system bodies, including Venus, Mars, Jupiter, Titan, the moon, and several comets. With the increasing interest in future small probe missions, mass spectrometers need to become even more versatile, lightweight, compact, and sensitive. For in situ exploration of ice giant atmospheres, the highest priority composition measurements are helium and the other noble gases, noble gas isotopes, including 3 He/ 4 He, and other key isotopes like D/H. Other important but lower priority composition measurements include abundances of volatiles C, N, S, and P; isotopes 13 C/ 12 C, 15 N/ 14 N, 18 O/ 17 O/ 16 O; and disequilibrium species PH 3 , CO, AsH 3 , GeH 4 , and SiH 4 . Required measurement accuracies are largely defined by the accuracies achieved by the Galileo (Jupiter) probe Neutral Mass Spectrometer and Helium Abundance Detectors, and current measurement accuracies of solar abundances. An inherent challenge of planetary entry probe mass spectrometers is the introduction of material to be sampled (gas, solid, or liquid) into the instrument interior, which operates at a vacuum level. Atmospheric entry probe mass spectrometers typically require a specially designed sample inlet system, which ideally provides highly choked, nearly constant mass-flow intake over a large range of ambient pressures. An ice giant descent probe would have to operate for 1-2 hours over a range of atmospheric pressures, possibly covering 2 or more orders of magnitude, from the tropopause near 100 mbar to at least 10 bars, in an atmospheric layer of depth beneath the tropopause of about 120 km at Neptune and about 150 km at Uranus. The Jet Propulsion Laboratory’s Quadrupole Ion Trap Mass Spectrometer (QITMS) is being developed to achieve all of these requirements. A compact, wireless instrument with a mass of only 7.5 kg, and a volume of 7 liters (7U), the JPL QITMS is currently the smallest flight mass spectrometer available for possible use on planetary descent probes as well as small bodies, including comet landers and surface sample return missions. The QITMS is capable of making measurements of all required constituents in the mass range of 1–600 atomic mass units (u) at a typical speed of 50 mass spectra per second, with a sensitivity of up to 10 13 $10^{13}$ counts/mbar/sec and mass resolution of m / Δ m = 18000 $m/\Delta m=18000$ at m/q = 40. (Throughout this paper we use the unit of m/q = u/e for the mass-to-charge ratio, where atomic mass unit and elementary charge are 1 u = 1.66 × 10 − 27 kg $1~\text{u} = 1.66\times 10^{-27}~\text{kg}$ and 1 e = 1.6 × 10 − 19 $1\text{e} = 1.6\times 10^{-19}$ C, respectively.) The QITMS features a novel MEMS-based inlet system driven by a piezoelectric actuator that continuously regulates gas flow at inlet pressures of up to 100 bar. In this paper, we present an overview of the QITMS capabilities, including instrument design and characteristics of the inlet system, as well as the most recent results from laboratory measurements in different modes of operation, especially suitable for ice giant atmospheres exploration.

中文翻译：

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用于冰巨大气探索的四极杆离子阱质谱仪

迄今为止，各种不同类型的质谱仪已被用于研究太阳系天体大气成分的任务，包括金星、火星、木星、泰坦、月球和几颗彗星。随着人们对未来小型探测任务的兴趣日益浓厚，质谱仪需要变得更加通用、轻便、紧凑和灵敏。对于冰巨行星大气的原位探测，最优先的成分测量是氦和其他惰性气体、惰性气体同位素，包括 3 He/ 4 He，以及其他关键同位素，如 D/H。其他重要但优先级较低的成分测量包括挥发物 C、N、S 和 P 的丰度；同位素 13 C/ 12 C, 15 N/ 14 N, 18 O/ 17 O/ 16 O; 和不平衡物质 PH 3 、CO、AsH 3 、GeH 4 和 SiH 4 。所需的测量精度主要取决于伽利略（木星）探测器中性质谱仪和氦丰度探测器所达到的精度，以及当前太阳丰度的测量精度。行星入口探针质谱仪的一个固有挑战是将要采样的材料（气体、固体或液体）引入仪器内部，仪器内部在真空水平下运行。大气入口探针质谱仪通常需要专门设计的样品入口系统，该系统理想地提供高度阻塞、在大环境压力范围内几乎恒定的质量流量入口。一个冰巨星下降探测器必须在一个大气压范围内运行 1-2 小时，可能覆盖 2 个或更多数量级，从接近 100 毫巴的对流层顶到至少 10 巴，在海王星约 120 公里和天王星约 150 公里的对流层顶下方的大气层中。喷气推进实验室的四极杆离子阱质谱仪 (QITMS) 正在开发中，以实现所有这些要求。JPL QITMS 是一款质量仅为 7.5 千克、体积为 7 升 (7U) 的紧凑型无线仪器，是目前最小的飞行质谱仪，可用于行星下降探测器以及包括彗星着陆器在内的小型天体和地面样本返回任务。QITMS 能够以每秒 50 个质谱的典型速度测量 1-600 原子质量单位 (u) 质量范围内的所有必需成分，灵敏度高达 10 13 $10^{13}$ counts/mbar/sec 和质量分辨率 m/Δm = 18000 $m/\Delta m=18000$ at m/q = 40。（在本文中，我们使用 m/q = u/e 作为质荷比的单位，其中原子质量单位和基本电荷为 1 u = 1.66 × 10 − 27 kg $1~\text{u} = 1.66\times 10^{-27}~\text{kg}$ 和 1 e = 1.6 × 10 − 19 $1\text{e} = 1.6\times 10^{-19}$ C。）QITMS 特征一种基于 MEMS 的新型进气系统，由压电执行器驱动，可在高达 100 bar 的进气压力下连续调节气流。在本文中，我们概述了 QITMS 功能，包括仪器设计和入口系统的特性，以及实验室在不同操作模式下的测量的最新结果，特别适用于冰巨行星大气探测。66 × 10 − 27 kg $1~\text{u} = 1.66\times 10^{-27}~\text{kg}$ 和 1 e = 1.6 × 10 − 19 $1\text{e} = 1.6\times 10 ^{-19}$ C，分别。）QITMS 具有由压电致动器驱动的新型基于 MEMS 的进气系统，该系统可在高达 100 巴的进气压力下连续调节气流。在本文中，我们概述了 QITMS 功能，包括仪器设计和入口系统的特性，以及实验室在不同操作模式下的测量的最新结果，特别适用于冰巨行星大气探测。66 × 10 − 27 kg $1~\text{u} = 1.66\times 10^{-27}~\text{kg}$ 和 1 e = 1.6 × 10 − 19 $1\text{e} = 1.6\times 10 ^{-19}$ C，分别。）QITMS 具有由压电致动器驱动的新型基于 MEMS 的进气系统，该系统可在高达 100 巴的进气压力下连续调节气流。在本文中，我们概述了 QITMS 功能，包括仪器设计和入口系统的特性，以及实验室在不同操作模式下测量的最新结果，特别适用于冰巨行星大气探测。) QITMS 具有由压电致动器驱动的新型基于 MEMS 的进气系统，可在高达 100 bar 的进气压力下连续调节气流。在本文中，我们概述了 QITMS 功能，包括仪器设计和入口系统的特性，以及实验室在不同操作模式下的测量的最新结果，特别适用于冰巨行星大气探测。) QITMS 具有由压电致动器驱动的新型基于 MEMS 的进气系统，可在高达 100 bar 的进气压力下连续调节气流。在本文中，我们概述了 QITMS 功能，包括仪器设计和入口系统的特性，以及实验室在不同操作模式下测量的最新结果，特别适用于冰巨行星大气探测。