Difference between revisions of "Online Spin Flip"

Revision as of 12:44, 24 July 2008

This main page of Spin Flip Control System for Hall A He3 Polarized Target.

Some Quick Links first:

• Shift Worker Quick Start
• Experiment Transversity
• Target Index Page

Introduction

Spin Flip System is designed for controlling Hall A Polarized He3 Target automatically flip spin direction during experiment run time. The physics goal is to reduce systematic false asymmetry, driven by experiment Transversity and d2n.

Core functions for this system are

1. Control the target spin flip consequence
2. Acquire and Record target spin state
3. Output target spin related information into DAQ system, therefore data stream
4. Interaction with human (Target Operator)
5. Communicate with related target software/hardware

For quick learning this system, please read Shift Worker Quick Start.

Physics of Spin Flip

Please refer to Thesis of Xiaochao Zheng, Charpter 4 Polarized He3 Target

System Structure

Spin Flip System Diagram

As Shown in the Spin Flip System Diagram, Spin flip system work closely with target hardware installations and DAQ system. This system is divided into 4 levels:

1. User interface : Display system status to user and take user command. Also notify user if an exception has occurred. User interface is based on Labview v7.1 environment.
2. Core : The core layer generate and execute a spin flip command on target, collect the respond, decide target status. If an exception occurred, it will try to handle the situation. Meanwhile, target information will be send to both user and DAQ.
3. Flip Confirmation : During a flip, target will radiate an NMR signal will be collected and processed through the pick-up coil, Lock-In Amplifier and a signal analyzer. The output will be current spin state, which is feed into system status manager.
4. Failure Detection : This layer will monitor status of Quarter-Wave Plate, which control laser polarization. It will ensure laser polarization is keep pumping the target in the correct direction.

User Interface

This section serve as a manual to all the GUIs.

Main Control

The main control signal provide a access point to every parts of the system. Also it controls the generation spin flip sequence.

Following sections will tour through all the controls in the order of left to right and up to down .

System Control Subpanel

• status indicator

The first control is the status indicator. There are 4 different states:

1. Initializing
2. Ready to Flip
3. Flipping
4. Error (the control will flash)

Left click of this control will show system status manager.

• Fool Proof Lock

If the lock is pressed down, it will show text "I'm Expert". Then every function & module will be accessible. Otherwise, it will show text "I'm Rookie". In this case user is only allowed to view the system status and clear errors.

The recommended setting for shift works are "I'm Rookie".

• Reset All

Warning : this function will affect target polarization and direction. Stop data taking before apply.

This button will try to load the system back to default status by executing following command in sequence:

1. turn off run simulation
2. Look for all quarter-wave plates connected, and automatically calibrate them. This process could take minutes depending on number of plates installed.
3. Ask for NMR sweep settings and reinitialize
4. Reboot EPICS interface
5. Start Auto Flip
6. Show sweep status
7. Show Log
8. Do a Flip to synchronize target hardware and logic electronics.

System Status Subpanel

• Sequence ID : This number will increase 1 after every rebooting this main control.

• Flip Count : Count of flips since last reboot.

• Last Reboot At : Time stamp when this code started running

• X Heart Beat : Heart Beat light of each thread with in this system. If one of them is halt, the whole code should be rebooted.

Spin Subpanel

• Spin Direction Indicator :

This indicator shows current spin state. There are three states:

spin of target is PARALLEL to holding magnetic field	spin of target is UNKNOWN	spin of target is ANTIPARALLEL to holding magnetic field
Value=+1	Value=0	Value=-1
AKA spin up	AKA spin unknon	AKA spin down

This is "expected spin", which is calculated by assuming every flip is successful since last calibration. If the NMR signal do not agree with this expectation, an error will be generated.

• Under Flip Indicator : Whether the target is under a flip

• Flip Now! Button : Execute A Flip Immediately, if system status is "Ready to Flip"

Automatic Flip Subpanel

• Auto Flip Set switch : Turn On or Pause Auto Flip.
• Auto Flip Indicator : Indicates whether auto flip is alive. There are two states of this indicator:

1. Auto Flip Alive
2. Auto Flip Suspended

Warning: When an error occurred, auto flip sequence will be paused and "Auto Flip", although "Auto Flip Set" switch is still on "ON" position. There are to method to recover auto flip sequence after the error is cleared:

1. Turn "Auto Flip Set" switch "OFF" then "ON" again
2. Wait 10min, then if there is no new error, flip sequence will recover automatically

• Flip Interval box : Time interval between two automatic flips. If their value is changed, waiting progress will be cleared to 0%.

Notice : This control will be disabled if Fool Proof Lock is ON.

• Waiting Progress Bar : If the bar reaches end, an flip command will be executed.

• X Time Stamp : There are 4 time stamp listed:

1. Current system time
2. Time when next automatic flip will happen
3. Last Flip started time
4. Last flip ended time

Notice : usually "Last flip ended time" - "Last Flip started time" < 5s

Modules and Functions Subpanel

• Sweep Setup Button : Show Sweep Setup window

Notice : This control will be disabled if Fool Proof Lock is ON.

• Sweep Status Button : Show Sweep Status window

• Phase Analysis Button : Show Phase Analysis window

• Laser Pol. Ctrl Button : Show Laser Polarization Control window

Notice : This control will be disabled if Fool Proof Lock is ON.

• Changing Pol. Indicator : Whether laser polarization is under changing.

• Simul. Switch : A toggle switch for whether actually carry on or simulate hardware operation and EPICS communication. If this switch is on, then

1. There will not be any GPRB operation, which means no RF send to target and no signal read back from Lock-In amplifier.
2. Every flip will be displayed to be successful.
3. EPICS communication is shutdown

Notice : This control will be disabled if Fool Proof Lock is ON.

• Show Status Button : Show System Status Manager window.

• Show Log Button : Show Text Log window

• Open Log File Button : Open the log file in windows notepad.

• Generate Report Button : Generate a User Report. User will be prompted to input a short comment, which will be added to top the report.

• Reboot EPICS Button : Reboot EPICS interface. No window/dialog will be showed.

Notice : This control will be disabled if Fool Proof Lock is ON.

System Status Manager

System Status Manager give target operator an quick overview of the full system. It follows the coloring rule.

Following sections will tour through all the controls in the order of up to down and left to right.

Error Handling Subpanel

• Sum of Spin and module check Indicator : This indicator shows OK if both spin check and module check indicator are OK; otherwise, it shows red ERROR.

• Now Time stamp : System Time

• System Status Indicator : It's a copy of system status from main control window. There are 4 possible states:

1. Initializing
2. Ready to Flip
3. Flipping
4. Error (the control will flash)

• Last Error Box : Last error time and description. During Error State, content of this box will be read out.

• Open Log Button : Show Text Log window.

• View Log File Button : Open the log file in windows notepad.

• Clear Error Button : By pressing this button, system status will be cleared from "ERROR" state to "READY to FLIP" state. Alarm will be turned off.

Warning : Clear Error Button do not solve the problem that causing the error. Target Operator should trace to and solve the source of the problem before turn on automatic flip again.

• Silence Alarm For 1hr Switch : just silent the audio alarm for 1 hour. After 1 hour, it will automatic pop up again.

Spin Check Subpanel

How to get more help

There are various of online help:

• When you move the cursor over the object and stay for a while, a help tip will be popped up.
• Right click a control, and choose "Description and Tips", a dialog containing a description will be shown. However, usually, description is no more than the tip.
• For developers and expert users, the Labview code is well commented. To some extent, the Code is the best documentation.

Exception Handling

Logic Electronics

Laser Polarization Control