Cornelius DPC 230 Specifications download pdf (Page 54)

48 SPCM Software

Fig. 79: SYNC frequency divider setting. The parameters determines the number of signal periods recorded in the

TCSPC mode

TDC Parameters

The TDC parameters determine the recorded time interval and the number of time channels in

the TCSPC mode and in the multichannel-scaler mode. The parameters are shown in Fig. 80.

Fig. 80: Left: TDC parameters. Right: Selecting the number of time channels from a list

‘Range’ is the recorded time interval. ‘Offset’ provides a shift of the results in time. ‘Channel

Number’ is the number of time channels. Values from 1 to 16384 can be selected from a list,

see Fig. 80, right.

Time/Channel is either the time channel width of the TDC (164.6 ps) or a multiple of this

value. Time/channel is set automatically depending on the selected ‘Range’ and ‘Channel

Number’.

Because ‘Range’ must by a multiple of the time-channel width of the TDC the parameters

‘Range’ and ‘Channel Number’ are automatically corrected to the nearest possible combina-

tion. If the selected number of channels would result in a ‘Range’ larger than selected the

value for ‘Range’ is automatically increased. If the desired ‘Range’ cannot be reached with the

selected number of time channels the width of the time-channels is increased, i.e. several TDC

channels are binned into one wider channel.

The ‘Multiphoton Detection’ button defines whether only one or several photons per signal

period are recorded in the TCSPC mode. Please be cautious when using TCSPC with mul-

tiphoton detection. Even when multiphoton detection is enabled a second photon cannot be

detected within the dead time of the detector. Multiphoton detection therefore does not neces-

sarily remove curve distortions by pile-up effects. On the contrary, dead-time effects can make

distortions even stronger, and less predictable than for single-photon detection.

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Cornelius DPC 230 Specifications Page 54