1. HAPPEX DAQ / ADC Tests Luis Mercado UMASS 4/17/09

2. Full DAQ System

3.  Crate currently used in electronics lab for testing.  Plan to move crate into the Hall in early June.  Left Arm Detectors.

4.  Will house Luminosity Monitor connections, Cavity Monitors and Right Arm Detectors.  Proper Lumi-ADC setup was tested Jan’08 to achieve minimum pedestal noise.

5.  Needs to be revived.  Will have different configurations with and without Qweak Crate to facilitate standalone tests.  Should we only use Helicity signals in this crate like during HAPPEX run?

6.  Recently underwent a test with 1 kHz MPS sequence.  DAQ starts to breaks down at 3 kHz.  Concluded we can run at 2 kHz, or 200 Hz with ovs of 10, or 240 Hz with ovs of 8.  Maybe higher but needs to be investigated.

7. Current Plans  Revive synchronization checks.  Replace many 16-bit ADCs with new 18-bit boards.  Basic DAQ should be ready for testing by mid-July.

8. Future Tests  High rate deadtime.  Checks of new helicity sequence board.  Synch checks.  Pedestal Studies (helicity-correlated noise).

9. Latest 18-bit ADC Tests

10. New 18-bit ADCs  Received four brand new boards a couple of weeks ago.  Performance matches previous tests with prototypes.  Will be receiving 10 more new boards by June 1st.

11. Testing of 18-bit boards.  Setting and recording proper pedestals offsets.  Studying pedestal noise with respect to gain setting (as low as 12ppm).  Testing linearity of current mode for use with Luminosity Monitors.  Comparing results with previous study done with 16-bit ADCs.

12. Integration Time (IT) Study  Have had problems in the past with gross nonlinearities at high end of ADC range.

13. Integration Time (IT) Study  Redid test using new 18-bit ADCs, with some changes: Sample more IT values by taking smaller steps up the IT ladder. More data points for higher IT values to get better error bar. Go up to 230-240K signal to see if it gets worse at the higher end.

14. Integration Time (IT) Study Residuals are less than 0.1% Local slopes vary by ~0.4%

15. Integration Time (IT) Study Residuals are less than 0.1% Local slopes vary by ~0.4%

16. PMT Linearity  Past tests have shown nonlinearities in PMT output dependant on input and gain.  Want to make sure we get similar results with new 18-bit ADCs.  Showed that results matched in good and bad linearity regions.

17. PMT Linearity (Formalism)  A PMT’s non-linear response can be expressed as follows:  Experimental asymmetry can be approximated:

18. Experimental Test Setup

19. PMT Linearity (w. 16bit ADC) Input = 12nA HV = 370 Output = uA B*N_0 = -5.25%

20. PMT Linearity (w. 18-bit ADC) Input = 12nA HV = 370 Output = uA B*N_0 = -5.14%

21. Good PMT Linearity Input = 2nA HV = 727 Output = uA B*N_0 = 0.7%

22. Good PMT Linearity Input = 2nA HV = 727 Output = uA B*N_0 = 0.77%

23. Ongoing Developments  Revive all HAPPEX DAQ crates and test their performance.  Will need to modify 18-bit ADCs to match replaced 16-bit boards.  Want to document good linearity regions for all available LUMI PMTs.

24. Acknowledgements  Krishna Kumar  Kent Pashke  Dustin McNulty  Robert Michaels  HAPPEX/PREX Collaboration