# Presentation: 742271

## Status of GRETINA

- David Radford
*ORNL Physics Division*
- JUSTIPEN                 February 2009

**Status of GRETINA**

## Status of GRETINA

- Outline:
-   Brief description of GRETINA
-   Status
-   Detectors, support, electronics, computing
-   Signal decomposition
-   Siting plans
-   Summary

- David Radford
*ORNL Physics Division*
- JUSTIPEN                 February 2009

**Status of GRETINA**

## GRETINA

- Gamma-Ray Energy Tracking Array for in-beam nuclear structure studies
- 28 highly segmented Ge detectors,
- 	 in seven groups of four
- 36-fold segmentation
- 	(6 azimuthal, 6 longitudinal)‏
- Tapered irregular hexagons
- Total  ~1 steradians
- Funded by DOE, under construction at LBNL
- Scheduled for completion (CD4) in March 2011

- 8 cm

- 9 cm

## Efficiency – Proper summing of scattered gamma rays, no solid angle lost to suppressors

**Efficiency – **Proper summing of scattered gamma rays, no solid angle lost to suppressors
**Peak-to-background – **Reject Compton events
**Doppler correction - **Position of 1st interaction
**Polarization – **Angular distribution of the 1st scattering
**Counting rate - **Many segments

- 3D position
- sensitive
- Ge detector

- Resolve position and energy of interaction points

- Determine
- scattering
- sequence

**Principles and advantages of gamma-ray tracking**

## GRETINA - People

- Contractor Project Manager:   I-Yang Lee (LBNL)‏
- GRETINA Advisory Committee (GAC):
- Con Beausang (U. of Richmond)‏
- Doug Cline (U. of Rochester)‏
- Thomas Glasmacher (MSU / NSCL)‏
- Kim Lister (ANL)‏
- Augusto Macchiavelli (LBNL)
- David Radford (ORNL) (Chair)‏
- Mark Riley (Florida State U.)‏
- Demetrios Sarantites (Washington U.)‏
- Kai Vetter (LLNL)‏
- Working Groups and chairs
- Physics			M. A. Riley   		(FSU)‏
- Detectors 		A. O. Macchiavelli 	(LBNL)‏
- Electronics 		D. C. Radford		(ORNL)‏
- Software 		 	M. Cromaz 			(LBNL)‏
- Aux. Detectors	D.G. Sarantites  	(WUSTL)‏

## Highlights of recent achievements

- Received CD2B/3B approval; construction of all systems started
- Received and tested the first two quadruple-detector modules
- Ordered detector modules 3 to 6 from Canberra-Eurisys
- New version of signal decomposition program & signal basis
- Achieved  ≤ 2mm position resolution
- Understood and eliminated preamplifier crosstalk and oscillation
- Completed signal digitizer and trigger modules
- Ordered first set of computers for decomposition cluster
- Developed a suggested national lab rotation schedule for the first round of experimental campaigns

## First Quadruple Cluster (Q1)‏

- Delivered  Dec 2006

**B-type**

**A-type**

**First Quadruple Cluster (Q1)****‏**

## Second Quadruple Cluster (Q2)‏

- Delivered  Dec 2008

**Second Quadruple Cluster (Q2)****‏**

## Mechanical Support Structure - under construction

-                    Spherical shell
- Rotation         Axle
- gear set

**Mechanical Support Structure - under construction**

- One hemisphere machined, tested and accepted

## Electronics

- Digitizer and trigger modules under test

- Digitizer module, 150 produced

- Designed, fabricated, and tested
-     digitizer modules (LBNL) and trigger modules (ANL)‏
-     -  Worked beautifully together on first try

**Electronics**

## Computing System

- 		-  Almost linear scaling up to dual quad-core CPUs
- 		-  A relief; had feared that algorithm may be limited by 				memory bandwidth
- Ordered first batch of 30 nodes for the decomposition cluster
- 		-  Dell, dual 2.8 GHz xeon, quad core, 8BG, 1U
- 		-  Final system will have 70 – 80 nodes

**Computing System**

## -  The heart of gamma-ray tracking.

- Tracking depends on knowing the positions and energies of the Compton interactions
- Digital pulse processing of segment data
- Determine number, position, & energy of multiple -ray interactions
- Uses data from both hit segments and image charges from neighbours
- Must allow for at least two interactions per hit segment
- Uses a set of calculated basis pulse shapes, on a predetermined grid
- Ideally suited to parallel processing
**  **Requires about 90% of CPU cycles used by GRETINA
- The major processing bottleneck, was greatest technological risk
- Baseline design specifies 20,000 gammas/s
- - allows only ~ 4 ms/crystal/node for decomposition

**Signal Decomposition**

## Examples of calculated signals: Sensitivity to position

- Hit segment

- Image charge

**Examples of calculated signals: Sensitivity to position**

- Image charge

**Signals colour-coded for position**

## Current algorithm is a hybrid: AGS + SQP
Pair-wise Adaptive Grid Search
~200,000 two-par. least-squares fits per segment (for energies)‏ in ~2 ms
Non-linear Least-Squares  (a.k.a. SQP)‏

Have also been developing Singular Value Decomposition
Collaboration with Tech-X Corp., funded under DOE SBIR
Developed SVD + SQP hybrid algorithm
		-  SVD on a coarse grid, with 250 eigenvalues
		-  Localize interaction regions
		-  Estimate number of interactions in each segment
Approx. 25% faster, but slightly poorer fits; further work planned
Also demonstrated speed-up of SVD algorithm by factor 30 to 40 using Graphics Processing Units (GPUs) rather than CPUs.

CPU time required :   	AGS   ~ O(500n)‏
							SQP   ~ O(n  + n2)‏		for  n  interactions	
							SVD   ~ O(n)‏

*Pair-wise Adaptive Grid Search*
- ~200,000 two-par. least-squares fits per segment (for energies)‏ in ~2 ms
*Non-linear Least-Squares  (a.k.a. SQP)**‏*
- Have also been developing *Singular Value Decomposition*
- Collaboration with Tech-X Corp., funded under DOE SBIR
- Developed SVD + SQP hybrid algorithm
- 		-  SVD on a coarse grid, with 250 eigenvalues
- 		-  Localize interaction regions
- 		-  Estimate number of interactions in each segment
- Approx. 25% faster, but slightly poorer fits; further work planned
- Also demonstrated speed-up of SVD algorithm by factor 30 to 40 using Graphics Processing Units (GPUs) rather than CPUs.
- CPU time required :   	AGS   ~ O(500n)‏
- 							SQP   ~ O(n  + n2)‏		for  n  interactions
- 							SVD   ~ O(n)‏

**Signal Decomposition Algorithm**

## Status of Signal Decomposition Algorithm

- Three orders of magnitude improvement in CPU time; now meets timing requirements
- Developed new optimized, irregular grid for the basis signals
**Developed method to accurately correct calculated signals for preamplifier response and for two types of cross talk**
- Incorporated fitting of signal start time t0
- Much improved fits (2 values)‏
- Can handle any number of hit detector segments, each with up to two interactions
- Although some work remains to be done, we have demonstrated that the problem of signal decomposition for GRETINA is solved

## Optimized Quasi-Cylindrical Grid

- Spacing arranged such that 2 between neighbours is approximately uniform,	 i.e. inversely proportional to sensitivity
- Optimizes RAM usage and greatly simplifies programming of constraints etc.

## Latest Decomposition Algorithm:  Data and fits

-   Red:  Two typical multi-segment events measured in prototype triplet cluster
- 	- concatenated signals from 36 segments, 500ns time range
-   Blue:  Fits from decomposition algorithm (linear combination of basis signals)‏
- 	- includes differential cross talk from capacitive coupling between channels

## Collimated Cs-source test

- Pencil beam of 662 keV:				  	Distribution of deduced interactions points throughout the 	crystal, from decomposition plus tracking algorithms

-  Position resolution:     σx = 1.5 mm;     σy = 1.7 mm

## Scanning-table coincident-data test

- Evaluated positions (red)
- Collimator position (blue)
- Position resolution:
-     σx = 1.2 mm;  σy = 0.9 mm
- Systemic error:
-     1.1 mm & 1.5 mm respectively.

## Workshop in Oct 2007, organized by the GAC
Plan for optimizing physics impact of GRETINA following completion in March 2011
Participation and presentation by Prof. Shimoura, U. of Tokyo; expressed interest in hosting GRETINA at RIKEN
Report prepared by GAC, submitted to DOE

Unanimous agreement on a plan for the first physics campaigns
Commissioning runs at LBNL, starting March 2001, coupled to BGS
Then rotate to other national laboratories, ~ 6 month campaigns
Suggested sequence for the first cycle:
MSU    -  NSCL
ORNL  -  HRIBF
ANL     -  ATLAS
“We look forward to further discussions with our Japanese colleagues and are excited about the possibility of future collaborations.”
Unique opportunities at RIKEN: Beams, auxiliary instruments, expertise

- Plan for optimizing physics impact of GRETINA following completion in March 2011
- Participation and presentation by Prof. Shimoura, U. of Tokyo; expressed interest in hosting GRETINA at RIKEN
- Report prepared by GAC, submitted to DOE
- Unanimous agreement on a plan for the first physics campaigns
- Commissioning runs at LBNL, starting March 2001, coupled to BGS
- Then rotate to other national laboratories, ~ 6 month campaigns
- Suggested sequence for the first cycle:
- MSU    -  NSCL
- ORNL  -  HRIBF
- ANL     -  ATLAS
- “We look forward to further discussions with our Japanese colleagues and are excited about the possibility of future collaborations.”
- Unique opportunities at RIKEN: Beams, auxiliary instruments, expertise

**Siting**

## 
Construction is proceeding, on schedule, on budget
Received  CD2B / 3B approval  Oct 2007

Signal decomposition problem is solved

Scheduled completion date:  2 March 2011  (Wed)‏

We have proposed a plan for the first round of physics campaigns

Next stage: Full 4 steradians
      GRETA received strong community support in LRP
“... construction of GRETA should begin upon successful completion of GRETINA”

- Construction is proceeding, on schedule, on budget
- Received  CD2B / 3B approval  Oct 2007
- Signal decomposition problem is solved
- Scheduled completion date:  2 March 2011  (Wed)‏
- We have proposed a plan for the first round of physics campaigns
- Next stage: Full 4 steradians
-       GRETA received strong community support in LRP
- “... construction of GRETA should begin upon successful completion of GRETINA”

**Summary**

## LBNL:
I-Yang Lee
Overall project manager and source of all wisdom!
A. Machiavelli, M. Cromaz, P. Fallon, M. Descovich, J. Pavan, many others
Detectors, DAQ, in-beam data analysis, simulations, electric field calc'ns, etc.
Sergio Zimmermann, John Joseph, Carl Lionberger, many others
Electronics, engineering, computing, etc.

GRETINA Advisory Committee and Working Group Leaders
Endless proposal writing, review preparation, working group meetings, conference calls, ...

John Anderson (ANL)‏
Trigger system
Karin Lagergren (ORNL / UTK)‏
Signal calculation code in C, Optimized pseudo-cylindrical grid
Tech-X Corp, especially Isidoros Doxas
SVD development

**I-Yang Lee**
- Overall project manager and source of all wisdom!
- A. Machiavelli, M. Cromaz, P. Fallon, M. Descovich, J. Pavan, many others
- Detectors, DAQ, in-beam data analysis, simulations, electric field calc'ns, etc.
- Sergio Zimmermann, John Joseph, Carl Lionberger, many others
- Electronics, engineering, computing, etc.
**GRETINA Advisory Committee** and **Working Group Leaders**
- Endless proposal writing, review preparation, working group meetings, conference calls, ...
- John Anderson (ANL)‏
- Trigger system
- Karin Lagergren (ORNL / UTK)‏
- Signal calculation code in C, Optimized pseudo-cylindrical grid
- Tech-X Corp, especially Isidoros Doxas
- SVD development

**Acknowledgements**

## Backup Slides

**Backup Slides**

## GRETINA – Collaborating Institutions

**Argonne National Laboratory**
- Trigger system
- Calibration and online monitoring software
**Michigan State University**
- Detector testing
**Oak Ridge National Laboratory**
- Liquid nitrogen filling system
**Data processing / signal decomposition software**
**Washington University**
- Target chamber

- Roles are defined by MOU’s with LBNL

## In-Beam test at LBNL

-  Derived 3D average effective position resolution  σ = 2.1 mm

- 3-crystal prototype
- 82Se + 12C @ 385 MeV
- v/c ~ 0.09
- 2055 keV (10+8+) in 90Zr

## In-Beam test at MSU

**2****+**

**E ********    (keV)**

- 36Ar at 86A MeV, v/c = 0.4
- Be target, 1mm thick
- PIII in coincidence with S800 	using time-stamp technique
-  Obtained effective position 	resolution of 2.2 mm
- 		Doppler correction:
- 		Crystal		10%
- 		Segment		 5%
- 		Tracking		 2%

**In-Beam test at MSU**

## ORNL Installation

***ORNL Installation***

- ORNL site CAD integration models

- Overview photograph of ORNL site

- LBNL railroad car design compatible with ORNL site
- No interference w/GRETINA at optimal RMS target location

## Cross-talk

- Differential cross talk arises from capacitive coupling between the inputs to the preamplifiers (some due to physical capacitance of the detector)
- Can be modelled well in SPICE, but needs to be carefully characterized in reality

## Fitting to Extract Cross-Talk Parameters

-   36 “superpulses” : averaged signals from many single-segment events (red)‏
-   Monte-Carlo simulations used to generate corresponding calculated signals (green)‏
-   996 parameters fitted (integral and differential cross-talk, delays, rise times) (blue)‏
-   Calculated response can then be applied to decomposition “basis signals”

## Why is it hard?

- Average segment ~ 6000 mm3, so for ~ 1 mm position sensitivity
-  two interactions in one segment: ~ 2 x 106 possible positions
-   two interactions in each of two segments:   ~ 4 x 1012 positions
-   two interactions in each of three segments: ~ 8 x 1018 positions
- 		PLUS energy sharing, time-zero, ...
- Underconstrained fits, especially with > 1 interaction/segment
- For one segment, the signals provide only 					~ 9 x 40 = 360  nontrivial numbers
- Strongly-varying, nonlinear sensitivity
-  2/(z)  is much larger near segment boundaries

**Why is it hard?**

## Comparison – Old Basis and Code vs. New

**Old**

**New**

- Distribution of deduced interactions points throughout the crystal

## Signal Decomposition

- GEANT simulations;
- 1 MeV gamma into GRETA
- Most hit crystals have one or two hit segments
- Most hit segments have one or two interactions

## Evolution of -ray Detectors

**The calculated resolving power is a measure of the ability to observe**
** ****faint emissions from rare and exotic nuclear states. **
- Taken from the NSAC 2002 Long Range Plan document, page 132.

**Evolution of ********-ray Detectors**

## Singular Value Decomposition

- The full signal -vs.- grid position matrix can be decomposed into the product of three matrices, one of which contains the correlations (eigenvalues).

**Singular Value Decomposition**

- =

-  MxN	             MxN	    NxN	        NxN

- N voltages

- M interaction sites

- A = UWVT

## Singular Value Decomposition

- The full signal -vs.- grid position matrix can be decomposed into the product of three matrices, one of which contains the correlations (eigenvalues).
- By neglecting the small eigenvalues, the length of the signal vectors (and hence computation with them) can be greatly reduced.

**Singular Value Decomposition**

- =

- 

-  MxN	             MxN	    NxN	        NxN               Mxn   nxn        nxN

- N voltages

- M interaction sites

- A = UWVT

## Singular Value Decomposition

- The full signal -vs.- grid position matrix can be decomposed into the product of three matrices, one of which contains the correlations (eigenvalues).
- By neglecting the small eigenvalues, the length of the signal vectors (and hence computation with them) can be greatly reduced.
- The more eigenvalues kept, the higher the quality of the fit.

**Singular Value Decomposition**

- =

- 

-  MxN	             MxN	    NxN	        NxN               Mxn   nxn        nxN

- N voltages

- M interaction sites

- A = UWVT

## 1  4 coverage,   28  120 detectors

- Greater resolving power by factors of up to 100
- GRETA is the most requested instrument at the next generation RIB facility     - RIA Facility Workshop,   March 2004

**From GRETINA to GRETA**

-  GRETINA

-  GRETA

-  Gammasphere

## How do extreme proton-to-neutron asymmetries affect nuclear properties, such as shell structure and collectivity?

What are the properties of nuclei at the limits of mass and charge? 

What are the properties of nuclei at the limits of angular momentum? 

Nuclear astrophysics, fundamental interactions and rare processes

- What are the properties of nuclei at the limits of mass and charge?
- What are the properties of nuclei at the limits of angular momentum?
- Nuclear astrophysics, fundamental interactions and rare processes

**Physics Opportunities**

## Gamma-Ray Tracking
	“... The construction of GRETA should begin upon successful completion of GRETINA. This gamma-ray energy tracking array will enable full exploitation of compelling science opportunities in nuclear structure, nuclear astrophysics, and weak interactions.”

- 	“... The construction of GRETA should begin upon successful completion of GRETINA. This gamma-ray energy tracking array will enable full exploitation of compelling science opportunities in nuclear structure, nuclear astrophysics, and weak interactions.”

**GRETA in the 2007 NSAC Long Range Plan**

## GRETA Cost and Schedule

- Could start in FY08, complete in FY16

-  As fast as allowed by detector production schedule.
-  No gap between GRETINA and GRETA construction
- Total cost is ~ M$42
-  Physics program to start 2011 with continued growth of capabilities.
-  Match FRIB schedule; GRETA will be ready when FRIB starts
-  Competing European project 1/3 AGATA plan to be completed in 2012

**Program**
**Starts**

**GRETA Cost and Schedule**