Online Spin Flip

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 Zhen, 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.
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.

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

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