8.2 Defining Pulses

While the basic setup of the pulse happens in the ASSIGNMENTS and, possibly, in the PHASES section, the definition of the pulses is done in the PREPARATIONS section.

Each pulse has at least three properties: a unique number, a function and a start position. Actually, pulses also need a length, so as long as the length is not set (or is 0) the pulse stays switched off. Here is an example of how to create a pulse, numbered 1, that is a microwave pulse, starts 100 ns after the trigger) and has a length of 250 ns:

PULSE_1:    FUNCTION = MICROWAVE,
            START    = 100 ns,
            LENGTH   = 250 ns;

As usual, most of the keywords can be abbreviated, PULSE_1: to PULSE1:, P_1: or P1:, FUNCTION to either FUNC or F, START to S, and finally, LENGTH to LEN or L. And, of course, for numerical values like pulse positions and times variables, complex expressions and functions can be used.

Pulse numbers can be chosen randomly - the only requirement is that the numbers are positive (including 0) and not larger than 2147483647 (2^32 - 1) (of course there always is some limitation by the device that won't allow to create that many pulses). Positions and lengths of pulses have to be positive (including 0). A pulse of zero length is invisible.

Each pulse must be assigned to a certain function (this is used to determine on wich output of the pulser the pulse will appear). The only exception is the TEGAM 2714A. if a channel number is assigned to a certain function than this function is automatically the function of each pulse (since this device only has a single channel).

If more than one pulser is used it must also be indicated which pulser is supposed to create the pulse. This is done by appending the # character, followed by the pulser number, to the PULSE keyword. Thus, if e.g. the pulse numbered 3 has to be created by the second pulser it must be created by a command like the following:

PULSE_3#2:   FUNCTION = RADIO_FREQUENCY,
             START    = 2 ms,
             LENGTH   = 8 ms;

Please note that in this case a RADIO_FREQUENCY function must have been defined for the second pulser.

Even when using more than one pulser the pulse numbers still have to be unique. If e.g. a pulse numbered 1 has been created for the first pulser it is not allowed to create a second pulse with the same number even when it is assigned to another pulser.

There are three additional properties a pulse can have. The first one is a constant amount of time the start position of the pulse will be changed by during the experiment, the corresponding keyword is DELTA_START(19). Second, there is a constant length change of the pulse, DELTA_LENGTH(20). And finally, there is the phase sequence to be used for phase cycling of the pulse - here the keyword is PHASE_CYCLE(21).

With these additional properties (using, for phase cycling of the pulse, the first phase sequence defined in the PHASES section, see above) the definition of the pulse would look like this:

PULSE_1:    FUNCTION     = MICROWAVE,
            START        = 100 ns,
            LENGTH       = 250 ns,
            DELTA_START  = 20 ns,
            DELTA_LENGTH = 35 ns,
            PHASE_CYCLE  = PHASE_SEQUENCE_1;

When setting the properties of further pulses the properties of pulses already defined can be used. This is done by specifying the name of the pulse (e.g. PULSE_1), followed by a dot and the property of the referenced pulse to be used. For example, if you want to create a second pulse that is also a microwave pulse, starts 300 ns after the end of the first pulse and is twice as long, you could write:

PULSE_2:    FUNCTION     = PULSE_1.FUNCTION,
            START        = PULSE_1.START + PULSE_1.LENGTH + 300 ns,
            LENGTH       = 2 * PULSE_1.LENGTH;

For the Rulbus pulsers there are several restrictions for the number of pulses that can be used. The MICROWAVE function can have a maximum of three active pulses at a moment while both the RADIO_FREQUENCY, the LASER (W-band configuration only) and the DETECTION function allow only a single active pulse. Moreover, for the J-band configuration (module rb_pulser_j) the RADIO_FREQUENCY and DETECTION can't start before the first MICROWAVE pulse. In the W-band configuration the DETECTION pulse only can have a length of 0 s or the length of the timebase (which is the default value if no pulse length has been set) and the DEFNSE pulse must always start at the very beginning of the pulse pattern (moreover, unless the function pulser_defense_pulse_mode() with the appropriate argument before the definition of the DETECTION pulse it is created automatically). Pulses can have a maximum length of about 167 ms and also delays between pulses (and before the start of a pulse) are restricted to this range of value. Finally, a RADIO_FREQUENCY pulse can only be created if the pulser is connected to the Rohde&Schwarz SML01 synthesizer (with SML-B3 option), which has a built-in pulse unit.

This document was generated by Jens Thoms Toerring on September 6, 2017 using texi2html 1.82.