CRYRING Linac RF

Hardware Description

In the CRYRING injector-linac two RF systems will be installed: One for RFQ, one for buncher.

The interface to the control system has to be build newly. The general outline of the linac RF installations will be very similar to the installations in the Unilac ( see becalsew), and the HITRAP. Therefore the interface hardware also is seen as a first prototype and feasability test for replacement of the existing Unilac control system interfaces.

RF generators are not monolithic equipment but are composed of several components:

A control loop unit provides an RF input signal to the power stage, which feeds its output into the cavity. The power stage more or less only amplifies the RF input. The control loop unit has to provide the power stage input with the correct amplitude, frequency and phase. The frequency is defined by the master reference frequency. Amplitude and phase (relative to the reference frequency) will be set locally. The control system mainly interacts with the control loop unit. Interaction with the power stage is reduced to control signals like power on/off and status messages, both handled by an PLC. In the present Installation in the Unilac a separate display unit presently provides a life display of the activities in the RF equipment, which is pulsed with 50 cycles per second repetition rate.

The RF generators will be operated in pulsed mode. Whenever a beam injection starts, a short RF puls is generated. Gate or trigger signals have to be provided to generate this RF puls.

Interface to the Equipment

Principles of Interfacing

Some basic general aspects have to be established between RF responsibilities and control system responsibilities:

• The control system interface will be implemented by an SCU crate, with common control system SCU-bus cards, like AD/DA and digital I/O cards.
• The control system interface will provide all nessecary signals and data.
  • The control system interface will provide appropriate gate and trigger signals (by decoding timing system information) for usage by the RF generator. No decoding of timing information in the RF hardware is needed.

Interface: Input / Output-Signals

Interfacing has to cover following data and signals (direction of input/output is as seen from equipment):

• data input (provide to equipment)
  • 2 set values
    • amplitude (digital value)
    • phase (digital value)
  • several digital control signals
    • generator on / off, RF on/off
      • the RF generator has two power switches:
        • generator: power up equipment, especially turn on tube heating
        • RF power
      • the control system will mirror this by the POWER-switch, implementing three states
        • OFF: equipment power off
        • STANDBY: generator is on (equipment is powerd, tube heating is on, ...), but no RF-power
        • ON: RF-power is on
    • reset, if foreseen in equipment
    • maybe more
• data output (read from equipment)
  • 1 acquisition value
    • amplitude (analogue value)
    • no readback for the phase will be provided
  • status readback
    • how many bits?
  • summary interlock signal
    • will this be provided? check, how to handle!
• trigger / gate signals to generate, and analyse, the RF pulse
  • a gate signal to control the RF pulse
  • a trigger signal to indicate that flat-top is reached
  • a trigger signal for AD conversion

The interfacing will be build according to ideas from the control system interfacing of the Unilc RF systems, see below, with two main modifications:

• Amplitude set value will be provided as digital value.
• Required pulses (RF-pulse on/off, trigger etc) will be provided by control system installation, no local decoding of timing)

The general outline of the RF installations in the Unilac, as well as in HITRAP, is shown in the following section. The control system interface has to cover the green interfacing crate (see HW schematics below).

Interface: Hardware Layout

The linac RF equipment will be controlled by an SCU, equipped with an AD/DA card and two digital I/O cards.

• one digital I/O card will be used for interaction with the control loop unit
  • this digital I/O Card will be used in addition to provide the HW trigger and gate signals
• one digital I/O card will be used for interaction with the power stage (controlled by a PLC, using other signal levels than the control loop unit)
• the AD/DA card will be used for reading the amplitude acquisition value

All triggers and gates will be derived from timing-events and will be provided by the digital I/O card. Puls and gate generation must not be implemented by software but processing must be purly in hardware (ECA-unit in combination with SCU-bus slaves). Software is only needed for configuration of the hardware elements. For an introduction, see Timing-Event Based Generation of HW-Triggers.

Information on the HW layout can be found in the Linac RF HW layout page.

Functional Aspects

Timing Control

The device must be operated in pulsed mode, which has to be driven by the timing-system. HW-triggering is assumed:

• A gate pulse must be provided to switch the RF pulse on and off. Another gate pulse, indicating the time when the RF pulse must be fully build-up, may be required by the control loop unit. These gate pulses will be derived by decoding timing-events. The FESA-class has to configure the timing-event decoding (see Timing-Event Based Generation of HW-Triggers).
• It is expected that keeping-warm RF pulses are not needed. In Sweden the RFQ was operated without such keeping-warm pulses. In Sweden a RF puls is generated only whenever the beam pulse is needed.
  • If keeping-warm pulses will be needed, it will be the task of the timing system to generate the corresponding timing-events (as is the case in the Unilac). The front-end equipment controller does not have to take care of local generation of keeping-warm pulses.

The above description of interface and keeping warm pulses is based on a meeting between controls people and RF experts (W. Vinzenz, J. Mohr) on 12. March 2013 and have been confirmed in a short on the fly meeting with the same RF experts on 20. June 2013.

An outline of the required timing is given below on this page.

Multiplexing

The RF will be set-up for one beam at a time only. However, the front-end FESA-class should implement multiplexed setting values in preparation for later operation of similar FESA-classes which have to implement multiplexing beams. Anyway, read-back data have to be acquired on a pulse to pulse basis. Both, setting as well as acquisition data, will have to be sent to or read from the hardware in real-time actions, which are triggered by timing-events.

In agreement with the responible persons for data generation, it is fixed:

• Multiplexing per beam process is required

The data generation responsible people assure that for all beam processes where the RF System is active

• Such beam processes always contain a time interval, indicated by appropriate timing-events, for off-beam operation of the RF-pulse (RF-pulse outside of the beam pulse, see section Off-Beam Operation)

Off-Beam Operation (Pause-Mode)

Generation of the RF puls must overlap the beam pulse to accelerate the beam. However, maintenance of the equipment requests also for an additional off-beam operation: Then the RF-puls is generated at a point in time when no beam passes the cavity:

• On-Beam (Pulse) Operation: RF pulse overlaps the beam pulse
• Off-Beam (Pause) Pause: RF pulse does not match the beam pulse

The point of time to start the RF pulse is indicated by timing-events, distributed by the timing-system. To switch from pulse operation to pause operation, the RF gate must be started by another timing-event. To do so, the front-end software must change the configuration of trigger generation. Preferably, the configuration of the of ECA-unit (the timing receiver) should be kept and only the configuration of the digital I/O card should be switched. To place the timing-event to start the off-beam RF-pulse generation is in the responsibility of the data generation which has to set-up the timing-system appropriately.

Switching between on-beam (pulse) operation and off-beam (pause) operation is by a property. In off-beam (pause) operation the setting values of the normal Setting-property will be used.

Local / Remote Operation

The control loop unit provides for local operation. Local operation is indicated to the control system by a status bit.

In local operation, the control system must ensure:

• Place the position of the RF-pulse outside of the beam pulse. The start of the RF-pulse must be the same as for the off-beam (pause) operation (see section Off-Beam Operation).
• The RF-pulse length is determined by data from a separate property 'LocalSetting', other than the normal Setting property

While the length of the RF-pulse is determined by a property, it must be assured that the RF-pulse never matches the beam-pulse. Therefore the front-end controller must assure:

• The RF-pulse must be cut-off always when a timing-event is decoded which indicates that the beam pulse will start soon

In local operation, the equipment ignores setting data from the control system for amplitude and pase, and ignores as well commands like generator on/off, RF on/off, and reset.. Amplitude and phase are adjusted using local knobs in the Equipment.

A special LocalSetting property must be provided to determine in local mode the parameter for

• pulse-length

The property LocalSetting will not be multiplexed.

In local operation, acquisition data like the current Amplitude, and status information, are provided by the equipment.

Power Up, Standby

RF equipment is equipped with two power switches:

• Generator On/Off: When switched on, the equipment is in standby state: The equipment is powered, especially tube heating is switched on. However, the RF generator will not produce RF output until the second switch (Power on) is switched to ON.
• RF On/Off: When switched to ON, the RF generator will produce RF-output.

When modeling the equipment, both switches should be combined to one, implementing three states:

• OFF: Both Switches off
• STANDBY: Generator On, Power Off
• ON: Generator On, Power On

When the POWER property is called, switching from one state to another may take some time. To indicate such a transition between two states when the POWER-state is requested from the FESA-device (e.g. when the POWER-propty is read) additional states have to be introduced. It is expected to provide at least two Transition states:

• TO_STANDBY: The equipment is switched from OFF to STANDBY (may take several minutes)
• TO_OFF: The equiment is switched from STANDBY to OFF (may take several minutes)
• Switsching between STANDBY and ON and vise versa is expected to be fast, no Transition state then will be needed (will be finished in few seconds)

Switching the equipment's power Switches (Generator On/Off, RF On/Off) is accepted in any sequence. No special care has to be taken in the FESA class to prevent from possible switching sequences. E.g., if the equipment is powering down (STANDBY to OFF, which means Generator On to Off), it is possible to Switch on the Equipment again - the Equipment simply then Switches to power up sequence.

Timing Outline

Multiplexed operation must ensure proper set-up of all parameters of equipment before each generation a RF pulse. A timing-system event, placed appropriately early, must be provided. The position of the RF pulse is determined by timing-events too. Position in time of the RF pulse is defined by a gate-pulse (RF-gate), providedby the control system interface. The position of the RF-gate is derived from timing events. A total of 6 timing events habe to be foreseen.

Reading of the acquisition data can be connected to the timing-event which is provided to end the in-beam RF pulse.

A schematic is given in the picture below.

Generation of the RF-gate has to be as follows:

When device is in remote operation:

• Pulse or Pause Operation (On-Beam / Off-Beam) set by property Setting
• setting wether on-beam or off-beam is multiplexed (specific per beam-process)
• generation of RF-gate:
  • case on-beam (pulse):
    • start RF-gate at event E
    • stop RF-gate at Event F
  • case off-beam (pause):
    • start RF-gate at event E
    • stop RF-gate at Event F

When device is in local operation:

• RF-gate must be generated off-beam (pause)
• length of RF-gate is set by property LocalSetting
• length of RF-gate is not multiplexed
• generation of RF-gate:
  • set length of RF-gate to LocalSetting.pulseLength
  • start RF-gate at event E
  • always cut off RF-gate at event D
    (in case the LocalSetting.pulseLength was set such that the RF-pulse would extend into the beam pulse)

Additional Functional Aspects

If any.

Property Layout

Proposition for Properties - not strict specification.

Multiplexing: Properties 'Setting' and 'Acquisition' represent multiplexed by beam process value items. However, operation of the CRYRING will start with one fixed value for the beam process.

property name	prop. type	field	type	unit	multi- plexed	meaning	impl
Status	status	status	DEVICE_STATUS	-	no	UNKNOWN/OK/WARNING/ERROR
		detailed_status	DETAILED_STATUS	-		see SPS and Controller register sets
Power	power	power	DEVICE_MODE_POWER (enum -> int)		no	should represent at least the states UNKNOWN/ON/OFF
						0 = UNKNOWN
						1 = ON
						2 = OFF
Reset	reset				cmd	Resets all errors
Init	init				cmd
Version	version				no
Setting	Setting	amplitude	double	volt	yes	Amplitude reference value
		phase	double	degree		Phase reference value
		pulse	bool	-		determines whether RF pulse is generated during beam (puls, RF acts on beam)or outside beam pulse (pause)
LocalSetting	setting	tpReglerLength	double	s	no	length of RF pulse in local operation
		samplePulseLength	double	s	no
		samplePulseDelay	double	s	no
Acquisition	acquisition	amplitude	double	volt	yes	Actual value of the amplitude
		amplitudeSet	double	volt		Reference value of the amplitude
		isAmplitudeOk	bool	-		1 = Amplitude OK / 0 = not OK
		phaseSet	double	degree		Phase reference value
		isPhaseOk	bool			1 = Phase OK / 0 = not OK
		pulseSet	bool			Pulse or pause

All acquistion properies implement an internal "onChange" behaviour.

Appendix A: Existing RF-Installation

The general outline of the linac RF installations will be very similar to the installations in the Unilac, and the HITRAP. RF generators are not monolithic equipment but are composed of several components:

A control loop unit provides an RF input signal to the the power stage, which feeds its output into the cavity. The power stage more or less only amplifies the RF input. The control loop unit has to provide the power stage input with the correct amplitude, frequency and phase. The frequency is determined by a master reference frequency. Amplitude and phase (relative to the reference frequency) will be set locally. The control system mainly interacts with the control loop unit. Interaction with the power stage is reduced to control signals like power on/off) and status messages, both handled by an PLC. A separate display unit presently provides a life display of the activities in the RF equipment, which is pulsed with 50 cycles per second repetition rate.

A control interface, developed by the RF department, is used to interact with the control loop unit, and in addition with the PLC and the display unit. As the central component for the interaction with the control system, this control interface is shown in green in the outline of the RF system.

The overall outline is shown in the following drawing. For a more detailed view see also schematics Alvarez-RF controls interface.

Functional Aspects

The CRYRING linac RF will use an control loop unit of similar type as the Unilac, and the HITRAP RF. For interfacing the RF installations, the control system interfacing has to provide connections, both input and output, which are compatible to the former interface (marked green in the above picture): It has to interact with the control loop unit as befor. This means: It must provide equivalent outputs, and has to read back information provided by the control loop unit.

The functionality of the control system interfacing should be oriented to the HITRAP installation rather than to the original Unilac installation. Although build to the same principles as in the original Unilac installations, the HITRAP installation already implements a significant improvement compared the older installations.

Handling of Pulse/Pause switching and Remote/Local switching has to be considered. Present implementation in the Unilac is as follows:

• Pulse/Pause: If switched to Pause, the RF-pulse is generated at a time when no beam is in the machine. In the Unilac this is at the beginning of the Unilac cycle (presently the timing system event 255 is used as an indicator)
  • Pulse/Pause mode can be set via the control system
  • Pause mode is also activated when the equipment is switched to local operation
• Remote/Local: If switched to local operation, control from the control system is disabled
  • In local operation the pulse generation is switched to Pause-mode, so in local operation the beam will not be affected by the RF generator

Appendix B: Meeting 4th Aug. 2014, LORF, CSCOHW, CSCOFE

This is an abstract of the meeting on 4. Aug. 2014 with LORF, CSCOHW, CSCOFE. Items should be integrated in the appropriate chapters.

In deutsch aus Zeitmangel:

• Wenn das Gerät auf Handbetrieb geschaltet wird, muss das Gerät automatisch in den Pause-Betrieb gehen. Das hat bisher das HW-Interface der Unilac-HF gemacht und muss (wahrscheinlich) in Zukunft die FESA-Klasse tun. Wann im Zyklus der Pause-Puls beginnt und wie lange er ist, muss dann entweder per Gerätekonstante oder, wahrscheinlicher, per Experten-Property eingestellt werden.

• Im Handbetrieb wird der vom Rechner vorgegebene Ampliduten-Sollwert ignoriert. Der Phasen-Sollwert ist unwichtig. Der Pause-Puls (das Gate) muss aber nach wie vor vom Rechner (SCU) bzw. vom Timing-Receiver (TR) vorgegeben werden.

• Die Länge und die Lage des Gate-Pulses, egal ob Puls- oder Pause-Betrieb, konnte am HW-Interface der Unilac-HF eingestellt werden. Diese Einstellmöglichkeit möchte man auch in Zukunft haben. Das muss dann per Software gemacht werden, da es keine lokalen Potis mehr geben wird.

• Man muss sich eine oder mehrere Experten-Properties überlegen, die
  • das Delay, gerechnet vom Event für den Pulsbetrieb, und die Puls-Pulslänge festlegen;
  • das Delay, gerechnet vom Event für den Pausebetrieb, und die Pausen-Pulslänge festlegen;

• Diese Einstellungen (des Gate-Pulses) sollen nur von Experten, nicht von Operateuren, vorgenommen werden. Allerdings sollten die Einstellungen auch von Operateuren zurückgelesen werden können.

• Es muss garantiert werden, dass die Einstellung von Start und Länge eines Gate-Pulses nicht in die zeitlich nächste Phase fallen. (Das kann für die FESA-Klasse schwierig werden!)
  • Ein Pause-Gate darf nicht in die Puls-Phase des selben Zyklus ragen, wenn man davon ausgeht, dass das Pause-Gate zeitlich vor dem Puls-Gate liegt.
  • Ein Puls-Gate darf nicht in den zeitlich nächsten Zyklus ragen.

• Da keine lokale Handbedienung mehr möglich ist, brauchen die HF-Experten Bedienungsmöglichkeiten vor Ort, um ihre Experteneinstellungen vornehmen zu können. Erste Näherung: FESA Navigator?

Die Experten-Properties sind im anschließenden Kapitel 'Property Layout' noch nicht enthalten.