Reduction of the jitter of single-flux-quantum time-to-digital converters for time-of-flight mass spectrometry

•We proposed single-flux-quantum (SFQ) time-to-digital converters (TDCs) for TOF-MS.•SFQ TDC can measure time intervals between multiple signals with high-resolution.•SFQ TDC can directly convert the time intervals into binary data.•We designed two types of SFQ TDCs to reduce the jitter.•The jitter is reduced to less than 100 ps.

We have been developing a high-resolution superconducting time-of-flight mass spectrometry (TOF-MS) system, which utilizes a superconducting strip ion detector (SSID) and a single-flux-quantum (SFQ) time-to-digital converter (TDC). The SFQ TDC can measure time intervals between multiple input signals and directly convert them into binary data. In our previous study, 24-bit SFQ TDC with a 3 × 24-bit First-In First-Out (FIFO) buffer was designed and implemented using the AIST Nb standard process 2 (STP2), whose time resolution and dynamic range are 100 ps and 1.6 ms, respectively. In this study we reduce the jitter of the TDC by using two different approaches: one uses an on-chip clock generator with an on-chip low-pass filter for reducing the noise in the bias current, and the other uses a low-jitter external clock source at room temperature. We confirmed that the jitter is reduced to less than 100 ps in the latter approach.