Instructions for Setting the T560 Digital Delay Generator for the Target Delay

Transcription

1 Instructions for Setting the T560 Digital Delay Generator for the Target Delay Important! These instructions are only to be followed by beam-line operators who have been trained to operate the target!! What you will need to Program the T560 To set the digital delay using a standalone PC you will need the following: A PC/laptop with Microsoft Windows installed. An Ethernet cross-over cable. One of these should be situated close to the T560 unit. The software that will allow your computer to talk to the digital delay box will need downloading to a directory on the above computer. The executable ( t560w.exe) can be found with the target documentation on the MICE web page at: 1

2 The T560 manual gives further information about the digital delay box and a copy of this can also be found at the above location. Setting the digital delay box will require you to make changes to your computer s IP settings. The settings given in this manual are specific to the delay box that is being used to generate the target delay. Other T560 units may require alternative IP settings see the official T560 manual. Clearly you should note down your own IP settings before changing them so that you can revert back to them after programming the T560 delay box. What Delay Settings Should I Use? Two of the four output channels on the T560 delay unit are used to control the target timing. The Channel A output is a delayed ISIS Machine Start (MS) signal and is used to provide a trigger signal to the target electronics. The Channel C is also a delayed MS signal and is used as a marker on the target rack oscilloscope. The Channel C signal is set to a constant delay of 4.6 ms so that it aligns with the start of the spill into which the target can be inserted. The ISIS MS signal for the target mechanism arrives 14.6 ms before beam extraction. However the target can take up to ~15 ms to reach the apex of its trajectory so the MS signal cannot be directly used to trigger the start of a target actuation. This is problematic because it is important that the target is inserted into the spill that directly follows the arrival of a MS signal. We call this the legal spill. To counter this timing problem the MS signal is used to trigger a delay. The period of this delay is timed to be slightly less than the period of the MS signal. The delayed signal then provides the target mechanism with a trigger that arrives at a known time before the next MS signal. Because this signal arrives slightly earlier than the next MS signal this gives enough time to allow the target to be inserted into the next legal spill. This delayed target trigger is created with the T560 delay unit. 2

3 The settings for the delayed Channel A output on the T560 are determined by the rate at which ISIS sends the MS signal to the target system. ISIS nominally operates at 50 Hz but the target is only inserted into 1 in every N of these spills where N is 50. Nominally these MS trigger signals arrive at a period of 64/50, 128/50 or 256/50 seconds (more generally 2 N /50). However since target Station 2 was brought online the period often changes to 64/40, 128/40 etc seconds. (Clearly this generalises to 2 N /40.) The raw MS signal provided by ISIS is a ve going signal that lasts for a couple of microseconds, this signal is cleaned up by some NIM electronics in the MICE DAQ rack before being passed onto the target electronics rack (still as a ve going signal of a couple of us duration) Before programming the delay on the T560 it is necessary to obtain the current period of the MS signal. This can be done by looking at the timing of the MS signal on a scope or, more easily, by asking the staff in the ISIS control room. It is often worth asking the staff if there is any reason if/why the signal period has changed because it is easier for them to set the signal period back to what it was than it is for you to reprogram the T560. Be aware that care needs to be taken when obtaining the period of the MS signal on a scope because the signal is of very short duration (us) compared to its period (s). It is VERY IMPORTANT that when the target is actuated it is inserted into the ISIS beam on the spill that immediately follows the arrival of the MS signal. The purpose of the marker signal on Channel C of the T560 is to help you ensure that this requirement is adhered to. The period of the MS signal is sometimes changed without warning, particularly when ISIS changes its mode of running during machine physics periods (i.e. ISIS switches from 50 Hz operation to 128/32 Hz). Therefore it is important during MICE operations to monitor the marker signal on the scope so that it can be ascertained whether the target is actuating into the correct spill. The reason for the importance of dipping into the correct spill is that the beam-loss trip thresholds are both adjusted and monitored separately on the ISIS spill that follows the arrival of the MS signal. Because of this the target is 3

4 only allowed to be inserted into the beam during these particular spills. The additional monitoring on these spills is for both the protection of the MICE target and the ISIS machine. Typically the delay on Channel A of the T560 is set for a period of MS signal period minus 10 ms This 10 ms of slippage allows enough time to trigger the target so that it can always intercept the ISIS beam during the next legal spill. Fine tuning of the target s timing to ensure that the target intercepts the beam at the correct point can be performed by the use of a second delay. The controls for the second delay can be found on the front of the target controller and the delay can be set from ms in 100 us increments. The details of how to do this can be found in the target operation s manual. As previously indicated the T560 should also be programmed to output a second marker signal of 2 ms duration 4.6 ms after the arrival of the MS signal on Channel C. This marker is then used to define the position of a legal spill and should be displayed on the target scope. If this marker is displayed on the oscilloscope AND used as the scope s trigger signal then the beam intensity trace that is aligned directly beneath the marker is the spill into which the target should be dipped. If the target is operational but the target is not seen to be dipping into the correct ISIS spill on the oscilloscope then this is indicative that the chosen delay setting is incorrect. Example of a typical T560 setting: If ISIS is providing a machine start signal at a period of 128/40 seconds (3.2 s) then the T560 channel A output needs setting to a delay of 3.2 s 10 ms = 3.19 s and 50 us duration. The marker setting on channel C is set to 4.6 ms delay and 2 ms duration. (These settings should remain constant.) 4

5 Setting up Communication with the T560 The first thing that you will need to do is to change your IP setting so that the computer can communicate with the T560. Go to your Control Panel and select Network Settings. The following screenshot assumes Classical View in Windows, however the menu is easy to find even if your Windows are set up differently. Next double click on your Local Area Connection to open this up. 5

6 Then select Internet Protocol (TCP/IP) and click on Properties. Next ensure that Use the following IP address is selected and then for the IP address type in with a subnet mask of All the other input fields can be left blank. Press OK. Note that you will almost certainly need to revert to your old TCP/IP settings after programming the digital delay box. 6

7 Close this window and close the Local Area Connection Properties Box to ensure that this change is updated on your system. Then connect the T560 to your computer using the cross-over Ethernet cable. After a few seconds your computer should notify you that it has successfully established a network. (Local Area Connection is Now Connected.) Programming the T560 At this point you can now start up the T560 configuration program t560w.exe. Double clicking on this executable should bring up a screen that looks like this. It is now necessary to ensure that the communication options are set appropriately before the program can send data to the T560. Double click on communications option and ensure that Ethernet is selected, the IP address is set to and that the port is set to Click OK 7

8 To ensure that everything is set up correctly press Refresh on the top left of the main screen. This should bring up a new window that gives details of the current settings of the T560. If you wish to load the current settings into the form of the main screen then press KEEP else press CLOSE. Note however, that if you press KEEP, you will still need to check all of the settings as described below. 8

9 Setting the T560 The trigger options for the target should never be changed as doing so could result in unreliable operation. The options should be set so that Source is External (It s a ve going signal) 50 Ohm is ticked Level is set to 0.5 Everything else is left blank Usually the target is triggered from the output on Channel A, and the marker pulse is set for Channel C. This can be confirmed by checking the BNC leads that exit from the T560 unit. Set the required Delay times into the delay fields in Channels A and C (Channel C is always 4.6 ms) Set the pulse Width time on channel A to 50 us Set the pulse Width time on channel C to 2 ms Ensure that the On box is checked on Channel A and C Ensure that the Active High Box is unchecked on Channel A (Important!) For channels B and D the forms should be left blank (The Active High check boxes can remain ticked though). All the settings in Burst Mode, Gate and Clock should also be left blank. By pressing the Send button on the top left of the main form this will send this information to the T560 and the T560 will now start operating from these parameters. However if the T560 is turned off then it will revert to its previous settings. To make the changes permanent go to File -> Save Setup. This should complete the programming of the T560. The T560 program can now be exited and your computer s IP settings should be returned to what they were previous to this exercise. 9

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