# HINS Clock Event Definitions and Initial Set-up

Bob Webber

March 27, 2007

## Introduction

There are three fundamental timing rates important to HINS Linac systems
operations.

> 1\) The ion source rate which needs to be steady and constant for
> stable ion source operating temperatures.
>
> 2\) The RF system pulse rate which may be less than the ion source
> rate, initially due at least to modulator charging power supply
> limitations.
>
> 3\) The accelerated beam rate which we allow to be set to a
> sub-harmonic of the RF rate.

A unique clock event is defined for each of these three fundamental
system rates. These events will have independently selectable repetition
rates and adjustable delays from the fundamental 10 Hz event of the
clock system. The philosophy is to provide common and adjustable event
references for systems linked to each of the fundamental rates.

New Rep Rate Generator hardware is expected to be available in summer
2007. Descriptions and definitions in this note assume the availability
of the new hardware and items that depend on it are noted in italics.

## Planned Clock System Implementation

The HINS accelerator in Meson will initially operate with nine clock
events. Six events, \$A9-\$AF, are triggered directly by the Rep Rate
Generator hardware; of these, four are fixed rate and two variable rate
events. These six events are synchronized with the fundamental 10 Hz
rate of the clock system (power line frequency divided by six) and each
occurs at its respective rate within microseconds of the corresponding
10 Hz event. The remaining three events, \$A6-\$A8, are triggered by
programmable delay timers individually referenced to one of the
\$A9-\$AF events. The rate of any event may or may not be different from
any other event except that the two variable rate events are inherently
coupled (*until new Rep Rate Generator hardware is installed*).

## Event Definitions

The event definitions are made as follows:

\$AF -- 10 Hz Event

-   fixed 10 Hz line-locked clock event (one-sixth of power line
    frequency)

-   triggered by GPIP Clock Generator

\$AE -- 5 Hz Event (*with new Rep Rate Generator only*)

-   fixed 5 Hz clock event

-   triggered by Rep Rate Generator hardware 2 µs after corresponding
    \$AF

\$AD -- 2.5 Hz Event (*new Rep Rate Generator only*)

-   fixed 2.5 Hz clock event

-   triggered by Rep Rate Generator hardware 4 µs after corresponding
    \$AF

\$AC -- "Rate M" Event

-   selectable by "Rate M" thumbwheel on Rep Rate Generator to 0.1, 0.2,
    0.5, 1, 2, 5, 10 Hz

-   *selectable to 0.2, 0.5, 1, 2, 2.5, 5, and 10Hz with new Rep Rate
    Generator*

-   triggered by Rep Rate Generator hardware 6 µs after corresponding
    \$AF

\$AB -- "Rate N" Event

-   COUPLED TO "RATE M" with present Rep Rate Generator!!!

-   selectable by "Rate N" thumbwheel on Rep Rate Generator to "Rate M"
    rate divided by 1, 2, 5, 10, 20, 50, or 100

-   *selectable to 0.2, 0.5, 1, 2, 2.5, 5, or 10Hz decoupled from "Rate
    M" with new Rep Rate Generator*

-   triggered by Rep Rate Generator 8 µs after corresponding \$AF

\$AA -- 1 Hz Event (*with new Rep Rate Generator only*)

-   fixed 1 Hz clock event

-   triggered by Rep Rate Generator hardware 10 µs after corresponding
    \$AF

\$A9 -- 0.1 Hz Event

-   fixed 0.1 Hz clock event

-   triggered by Rep Rate Generator hardware 12 µs after corresponding
    \$AF

\$A8 -- Ion Source Event

-   triggered by Ion Source Event Trigger delayed timer channel

-   referenced to any Rep Rate Generator hardware triggered event

\$A7 -- RF Event

-   triggered by RF Event Trigger delayed timer channel

-   referenced to any Rep Rate Generator hardware triggered event

\$A6 -- Beam Acceleration Event

-   triggered by Beam Event Trigger delayed timer channel

-   referenced to any Rep Rate Generator hardware triggered event

It is expected that the \$A8 Ion Source Event will be referenced to the
10, 5, or 2.5 Hz event (\$AF-\$AD respectively), the \$A7 RF event
referenced to the \$AC "Rate M" Event, and the \$A6 Beam Acceleration
Event referenced to the \$AB "Rate N" Event.

Ion source referenced systems are to be timed relative to the \$A8
event, RF referenced systems relative to the \$A7 event, and beam
referenced systems relative to the \$A6 event.

## 

## "Start of Beam" Definition and Event Setup

The klystron modulator(s), ion source, LLRF, and possibly other systems
require triggers as much as several milliseconds in advance of "Start of
Beam" time. To accommodate these requirements and to provide that all
systems monitoring clock events can know precisely when to expect beam,
[the time of "Start of Beam"]{.underline}[^1] [is formally defined to be
5000 microseconds (µs) after the respective \$A6 Beam Acceleration
Event]{.underline}. Additionally, the [nominal]{.underline} time of the
\$A6 Beam Acceleration Event shall be 5000 µs after the corresponding
\$AF 10 Hz Event.

This implies that the nominal "Start of Beam" time occurs 10,000 µs
after the corresponding \$AF 10 Hz Event. For diagnostic and system
studies purposes, the "Start of Beam" may be moved relative to the \$AF
event by changing the \$A6 Beam Acceleration Event trigger delay;
nevertheless the "Start of Beam" shall remain 5000 µs after the \$A6
event itself. Delays for the \$A8 and \$A7 event triggers will need to
be set as required relative to the \$A6.

Trigger delays to generate the \$A8 Ion Source Event and the \$A7 RF
Event are somewhat arbitrary, since most system triggers have subsequent
programmable delays from their respective event. The \$A8 and \$A7 event
trigger delays should be ≥100 µs so these events are well separated from
the fixed rate events and yet small enough to allow systems to take
advantage of the time until "Start of Beam".

## RF System Timer Assignments and Example of Initial Settings

The following assumes the nominal "Start of Beam" time, 10,000 µs from
the corresponding \$AF event, and a 500 µs delay of the \$A7 RF Event
from the \$AF.

The klystron pulse transformer rise-time is assumed to be 400 µs,
superconducting cavity RF rise-time is assumed to be 500 µs, and these
two are assumed to be sequential with no overlap. Therefore, the
modulator flattop must be attained 500 µs in advance of "Start of Beam",
i.e. by 9500 µs relative to the corresponding \$AF event.

Nominal delays are shown in the table below for a 1 millisecond beam
pulse starting at the nominal 10,000 µs "Start of Beam" time. Modulator
pulse width setting must be beam pulse length plus transformer rise plus
cavity RF rise = 1.9 ms. Relative to the \$A7 event, things occur at
these times: modulator trigger at 5350, center of modulator pulse at
9550, beginning of video pulse flattop and beginning of RF power at 9550
-- pw/2 + 400 = 9550-950+400 = 9000, and beginning of cavity RF flattop
at 9500. With \$A7 set to 500 after \$AF, cavity RF flattop begins at
10,000 relative to \$AF as required.

**VME Crate 8-Channel Delay Timer Assignments and Initial Settings**

  ----------- -------------------- ------------- ------------ --------------
  **Channel   **Assignment**       **Reference   **Nominal    **Nominal
  \#**                             Event**       Delay**      Width**

  Channel 0   Modulator Trigger    \$A7          5350 µs      10 µs

  Channel 1   Forward Power RF     \$A7          9000 µs      Desired RF
              Interlock Gate                                  Pulse Width

  Channel 2   Reverse Power RF     \$A7          9500 µs      Desired RF
              Interlock Gate                                  Pulse Width
                                                              -500 µs

  Channel 3   RF Interlock         \$A7          8900 µs      10 µs
              Digitizer Trigger                               

  Channel 4   RF Gate              \$A7          9000 µs      Desired RF
                                                              Pulse Width

  Channel 5   \$A7 RF Event        \$AC          500 µs       10 µs
              Trigger                                         

  Channel 6   N/A                  TBD                        

  Channel 7   Scope Trigger        \$Ax          User choice  10 µs
  ----------- -------------------- ------------- ------------ --------------

## Timing Requirements from Systems Experts

### Modulator Timing Requirements Per Chris Jensen

The modulator trigger pulse sent from the control system (1us pulse
width or more) starts the bouncer circuit ringing and the CENTER of the
modulator output pulse is fixed at roughly 4.2 ms (need to verify) after
the trigger pulse. The modulator output pulse width variable is set
locally or by the modulator interlock computer, NOT by the timing
system. The modulator pulse width setting needs to be 400 microseconds
greater than the desired video pulse flattop length to account for pulse
transformer rise time and this additional 400 us is not centered but
added to the beginning. For example, a video pulse flattop of 3 ms
requires the modulator pulse width setting to be 3.4 ms and the start of
the flattop relative to the modulator trigger will be at
4.2 ms + 0.4 ms - 0.5 \* PulseWidthSetting, e.g. 4.2 ms + 0.4 ms - (3.4
ms/2) = 2.9 ms.

To keep start of modulator pulse flattop fixed in time when modulator
pulse width is changed, the modulator trigger must be changed by an
amount that is one-half and the same sign as the change in pulse width.
For example, a pulse width increase of 1000 µs calls for a 500 µs later
trigger time.

### Ion Source Timing Requirements

Chuck Schmidt claims that ion source timing requirements can be
accommodated by an ion source trigger 5 milliseconds in advance of
expected time of start of beam.

### Low Level RF Timing Requirements

Brian Chase requested up to 10 milliseconds advance timing before "Start
of Beam" to accommodate possible pulse-by-pulse active reference line
phase measurements.

[^1]: To be unambiguous at the microsecond level, "Start of Beam" for
    any machine cycle is defined as the time at which the front edge of
    the beam pulse exits the MEBT Chopper.