Gammasphere

ATLAS Users MeetingAugust 8, 2009

2

Gammasphere Array

P/T ~ 55% (insitu)

P/T ~ 15%

Note: 68% P/T achieved on bench.

Fully loaded, Gammasphere can accommodate 108 Compton suppressed spectrometers

Detector Status

Goal: Provide user with 101 Ge detectors on continuing bases (maximum possible at FMA).

Continued cycles of annealing, Ge detector becomes a candidate for annealing when FWHM > 3 keV - anneal 15-20 detectors every 3-4 months.

HV-Filters for segmented GS Ge detectors are no-longer available in market, and home-made has been tested and used.

BGO bases continue to fail. Prototype replacement for bases using surface mount components have been constructed. Replacement of bases to begin in 2010 (replacement parts on order).

Bottom line – Gammasphere detectors are aging and need more attention to assure optimal use of device.

Experiments

A total of 18 experiments with 89 days (43% of total ATLAS running time) of beam time have been performed in FY08.

15 Experiments have been performed in FY09.

32 Gammasphere publications appeared thus in 2008.

Recent Upgrades

New VME based acquisition system has replaced original DAQ. Data can be written to USB drives. Throughput issues for high-spin measurements have been

addressed with new VME processor (T. Lauritsen and C. Lionberger).

Upgradeable path should allow us to write 3Mbytes/sec of data equivalent to 6 Exabyte tapes writing simultaneously.

System is extremely stable (rarely crashes or hangs up).

Online ROOT based analysis package GSSort, has been developed using the Root package from CERN.

BGO base replacement to begin in 2010 – not sooner due to long lead time on some parts.

Electronic logbook (ELOG) has been implemented.

Phase I construction of Digital Gammasphere has begun.

6

Gammasphere Limitations

Count Rate Limitations processing time for Ge shaper is ~10sec which gives ~6% pileup at

10,000 cps, 20% pileup @ 30,000 cps and ~30% pileup @ 50,000 cps. Solution – reduce Ge shaping time allows higher rates. Measured

resolution degrades from 2.3 keV to 3.0 keV when going from 10 sec to 2.3 sec processing time.

Trigger limitations Gammasphere is dead for at least ~ 25sec for triggered events. Single and 2-fold Ge triggers saturate Gammasphere rate capability. Readout can only be aborted at main (300-1500ns) and late (6sec) Solution – flexible trigger incorporating triggerless option.

7

Digital Gammasphere

Decreasing processing time of Ge shaper from ~10 to ~2sec should allow Ge to run at 40,000 cps with same throughput.

Trigglerless option will improve throughput limits imposed by current trigger.

These upgrades would allow Gammasphere to take data in excess of 10 times current limited rates.

Adaptive pileup algorithm could increase throughput further.

Extended Gammasphere reach in these areas of interest. 100Sn region Z > 100 Exotic modes (Hyperdeformation)

Competitors are implementing or retrofitting arrays with digitizers e.g. Juroball, Clarion, SeGA, Tigress, Gretina, Agata.

Digital Gammasphere

Met with GRETINA group to discuss using GRETINA digitizers as basis for digital Gammasphere (May 2008).

Two stage plan:– Digitize only high-resolution Ge channel and read as external

data. Compton suppression done by VXI electronics (Phase I)– Full digitization of both BGO and Ge detectors (Phase II)

Submitted LDRD proposal to ANL for startup money (denied)

Project seeded with $125k from PHY base budget to begin Phase I (June 09).

Project underway July 09 with GS scientific staff, Phil Wilt (PHY) and John Anderson (HEP).

9

Phase I - Instrument Gammasphere with Gretina Digitizers

Provide G R ET IN A D IG IT IZ ER B LO C K D IAG R AM

C H 0 FE /A D C

D A C 0 O U T

LE D O U T

A U X IO IN

F R O N T B U S IO

S E R /D ES IO

C C O U T

E V E N T F IFO

50M Hz REF CLK

50M Hz RCLK

C H 1 FE /A D C

C H 9 FE /A D C

D A C 1 O U T

V M E C T R L

&

I/O

M A IN FP G A

X C 3S 5000 -5F G 900

(6 33 U S E R I/O )

100M H z C LO C K D IS T

M U X

• Instrument current Gammasphere electronics with Gretina digitizers.

• 16 Gretina digitizer boards

• 2 VME crates – 6 backplanes (4 digitizers/backplane).

• 3 Gretina trigger modules.

• New VXI board to sit in GS master crate to pass GS clock and trigger information to DGS.

• System will also be stand alone and can be used with other detector systems i.e. 80x80 DSSD.

GS and DGS will take data simultaneously, triggered by GS and using syncronized time stamps. Recover GS pileup in DGS.

10

Phase II – Full Digital Gammasphere A Gammasphere module provides up to 10 signals for processing– 1 Ge central contact– 2 Ge outer contacts– 7 BGO signals

One Gretina digitizer card could instrument one Gammasphere Module.– Most expensive option ~ $350k for digitizers alone.– Is full digitization of individual BGO energies necessary?

One Gretina digitizer card could instrument 3 Gammasphere Modules– Digitize 3 signals, Ge central contact, 1 side channel, BGO Sum Energy– Generate externally BGO hit pattern to enable nearest neighbor suppression.– Individual BGO energies not available.

One Gretina digitizer card could instrument 2 Gammasphere Modules– Digitize 5 signals - Ge central contact, 1 side channel, 3 multiplexed BGO signals

(2,2,3) – individual BGO energies available.

11

Phase II – Slow Control and Signal Distrubution

NOW

UPGRADE

Slope Box

Grey Cables carry all control and signals to shack

BGO MultiplexerData from HpGe and BGO 100 Mhz (LBL)

Local VME Digitizers

Optical Link

To event builder

Master Slow Control

Workstation

12

Slopebox Control (Phil Wilt)

13

CARIBU and Gammasphere

Reaccelerated beams– Coulomb Excitation (Safe/Unsafe)– Transfer– Deep Inelastic– Fusion Evaporation (?)

Decay studies (gamma/beta)– Decay from high-spin state– Angular Correlations - spins– Polarization (Gretina) – multipolarity

New Equipment– Tape Station– Electron detectors - decay coincidence, multipolarity)– Fast Scitillators (LaBr:Ce) – state lifetimes– Plunger - lifetimes– Heavy-ion Counter (Super-Chico, Annular DSSD) - Coulex