A tandem mass filter consists of two low‐resolution mass filters arranged in series that operate with a small offset between their mass windows. In principle, the overlap of the two individual mass windows defines the tandem window. Tandem operation provides improved resolution and transmission compared to a single mass filter operated with the same mass window. The improvement in transmission is owed to the larger acceptance of the low‐resolution quadrupoles. The tandem filter resolution and transmission are adjusted by changing the amount of offset separating the mass windows of the individual filters. Sine wave systems create this offset through voltage changes. Digital tandem mass filters depart from convention because they do not change voltage. The tandem mass window is created when the individual filters are operated with two slightly different duty cycles. Both quadrupoles operate at the same frequency, phase, and voltage. When the frequency, phase, and voltage of each quadrupole are identical, there theoretically are no changes to the Mathieu parameters to cause ion excitation and loss during transition between the quadrupole pair. The work presented here shows that a fixed AC voltage digital tandem mass filter can only operate in higher stability zones. However, unlike sine mass filters, the mass range of a digital system is not limited. This makes the digital tandem mass filter feasible as a commercial product. For the tandem digital mode to be successful, the duty cycles of each quadrupole must be precisely controlled because the duty cycle differences required to shift the mass windows are small. The creation of these mass window offsets requires waveform generation that can obtain high duty cycle resolution. Our method of generating waveforms can meet this demand; however, modifications to our current printed circuit board must be made. These modifications are minor and will be discussed.

中文翻译：

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新型数字串联四极杆质量过滤器的计算评估

串联质量过滤器由两个串联的低分辨率质量过滤器组成，它们在质量窗口之间的偏移很小。原则上，两个单独的质量窗口的重叠定义了串联窗口。与在相同质量窗口下运行的单个质量过滤器相比，串联操作提供了更高的分辨率和透射率。传输的改善归功于低分辨率四极杆的广泛接受。串联过滤器的分辨率和透射率通过更改将各个过滤器的质量窗口分开的偏移量来进行调整。正弦波系统通过电压变化产生这种偏移。数字串联质量过滤器违反了常规，因为它们不会改变电压。当单个过滤器以两个略有不同的占空比运行时，将创建串联质量窗口。两个四极杆都以相同的频率，相位和电压工作。当每个四极杆的频率，相位和电压相同时，理论上不会改变Mathieu参数，以在四极杆对之间的过渡期间引起离子激发和损耗。此处介绍的工作表明，固定的交流电压数字串联质量过滤器只能在更高的稳定性区域中运行。但是，与正弦质量过滤器不同，数字系统的质量范围不受限制。这使得数字串联质量过滤器可以用作商业产品。为了使串联数字模式成功，每个四极杆的占空比必须精确控制，因为移动质量窗口所需的占空比差异很小。这些质量窗口偏移的创建需要能够获得高占空比分辨率的波形生成。我们生成波形的方法可以满足这一需求。但是，必须对我们当前的印刷电路板进行修改。这些修改很小，将进行讨论。