Cassini MIMI Investigation at Fundamental Technologies

 Historical MIMI Memos and Notes

Presentation by K. Heerlein at MIMI team meeting, October 1994

(K. Heerlein, Max-Planck-Institut Lindau)

Equipment for Testing LEMMS

2. Input Pulses for the Nine Energy Channels

2.1 Tail Pulse Generator

2.2 Main Description

The tail pulse generator is able to generate ten separate adjustable tail pulses. The adjustment can be made directly at the device or with a PC.

For each channel, the following can be adjusted:

• the energy level(in four ranges):

  Range	Max Energy	Min Energy	Step Width
  1	99.9 MeV	10 MeV	100 keV
  2	9.99 MeV	1 MeV	10 keV
  3	999 keV	100 keV	1 keV
  4	99.9 keV	~0 keV	0.1 keV

• the delay time of the pulse:
  • manual in the range 0 to 99.99 ms
  • per PC in the range 0 to 160 ms

In addition, it is possible to change the pulse cycle time for all channels in the range of about 100 Hz to 1 MHz.

It is also possible to trigger pulses by an external signal.

2.3 Structure

The tail pulse generator consists of four different mainboards and three daughterboards. The connection between the boards is made by a bus system:

2.3.1 Clock/Cycle Keyboard

On this board the clock frequency (100 MHz) for the delay time adjustment of the tail pulses is generated. Furthermore, it contains the logic to adjust the cycle time of the pulses. This time is divided from the clock. The dividing ratio is given by the PC or it can be manually adjusted on the front panel.  In addition, the cycle time can be given by an external source.

To select between manual/PC or external adjustment there is the 'Cycle Keyboard' which is mounted on the front panel.  On this board one can switch between the two inputs (intern/extern); the cycle time can be adjusted by a poti, and two LEDs show if the PC is programming.

The adjustment range is (intern):

--for manual mode:  about 380 Hz to 1 MHz
--for PC:  85 Hz to 1 MHz

The above values depend on the pre-divider for the 100 MHz and can be preselected by a dipswitch on the board.  The maximum frequency is dependent on the time constant of the pulse.

The adjustment by PC has priority and ignores the manual selected values.

2.3.2 Manual Control Board and Key Unit

The manual control board contains the complete logic to control the generator.   The channel settings can be made by the key unit board which is mounted on the front panel and connected to the manual control board by a flat cable.  The adjusted values for a chosen channel are transmitted by the bus system.  The data acknowledge signals are created by an EPROM.

How to program in manual mode (keys on front panel):

1. In 'run mode' select the channel you want to program.
2. Press 'program' (now all values for the channel settings are directly transmitted to the selected channel.
3. Select the channel settings:
   -delay time between 0 and 99.99 ms
   -energy level range (99.9MeV/9.99MeV/999keV/99keV)
   -energy level 0-99.9 (9.99/999)

In the power up situation all channels are programmed to 'default values.'

2.3.3 Interface Board

This board functions as a buffer for the incoming data signals from either PC or manual control. If there is programming by PC, shown by a 'PC PROGRAMMING' signal, only the PC signals will lead to the bus and therefore to the channels. Otherwise data from manual control will be transferred to the bus (PC has priority).

2.3.4 Channel Board and Tail Pulse Former

The generation of the pulses is made on this board. The received data is latched processed and then transferred to the onboard Tail Pulse Former. This Tail Pulse Former is in a metal case for electromagnetic shielding.

2.4 Block Diagram

(Click on figure for larger version.)

3. Motor Control

To control the motor, it is foreseen to use VTT equipment. If it is possible, the used control program should be implemented to the test program, so that only one PC is used to control the motor and LEMMS electronics.

4. Data Acquisition of Housekeeping Data

For data acquisition of the housekeeping data during testing, there will be used an i/o card with differential analog inputs.

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