Examples of Delay Element Response to Photomultiplier Pulses

As they say, the proof of the pudding is in the eating...

The pictures on this page show the incident pulse, and the delayed pulse. The source of pulses was a Burle 8575 PMT, which delivers pulses with roughly the same rise and fall time of the IceCube PMT choice.

The delay element can typically be accused of diminishing the rise-time (and fall time) of the waveform, stretching out the waveform, reducing pulse-pair resolution, and perhaps introducing a distortion onto the waveform.

Some images have associated waveform file links. The waveforms were sampled at 2.5 GS/s. If every eighth sample were extracted from the file, the equivalent sampling rate would be comparable to the sampling rate planned for the IceCube experiment. Additional waveform files can be provded on request, except that the PCB delay line is no longer available for measurements since it was returned to Wisconsin.

Each image is in turn a link to a higher quality PDF image.

Examples of response of RG-62/U Coax delay.

The input of the coax is matched to the source impedance with a 100 ohm parallel resistor. The output of the coax is matched the 50 ohm oscilloscope input with a 51 ohm series resistor. The match is not perfect, however, the reflections are small, and absorbed by the back-termination of the PMT base.

Input waveform data file in spreadsheet format.
Output waveform data file in spreadsheet format unavailable.

Input waveform data file in spreadsheet format.
Output waveform data file in spreadsheet format.

Examples of response of Printed Circuit Board delay.

This strip-line was fabricated with ordinary FR-4 laminate, consequently, the waveform is more distorted than it would be with the low-loss laminate example below.
The input of the strip-line is matched to the source impedance with a 95 ohm parallel resistor. The output of the coax is matched the 50 ohm oscilloscope input with a 55 ohm series resistor. The match is not perfect, however, the reflections are small, and absorbed by the back-termination of the PMT base.

Input waveform data file in spreadsheet format.
Output waveform data file in spreadsheet format.

Examples of response of Lumped Delay Line.

The sample delay line was manufactured by Data Delay Devices for the KAMLAND experiment. The impedance of the device is taken to be 62 ohms. The input is matched with the appropriate shunt resistor, and the output match with a 12 ohm series resistor to a 50 ohm oscilloscope input.

A feature of the response of the sample lumped delay line is the reverse polarity feature that preceeds the leading edge of the waveform.
Another feature is the lumped delay line is the smoothing and stretching out of the waveform.
The "Fall" and "Width" measurements performed by the oscilloscope may be helpful assessing the behavior of the component.

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