First complete test measurements of the AGATA Core _ Pulser Assembly

.

• AGATA Core Pulser, Segments Bulk Capacitances (First measurements of the Pulser Core / Segment Ratio) • Real transfer function measurements of the AGATA Pulser_Core and Segments preamplifiers

• Core recovery from saturation ( with SHD_C ON / OFF )

• Pulser dynamic range and intrinsic pulser energy resolution for core & segments

• Conclusion, hints to improve the characteristic.

• G. Pascovici on behalf of preamplifier & detector teams

Cologne, March 16, 2006

CSPs for the first AGATA_Detector Core Tests

Specs IKP-Cologne(a) (FET_BF862)

IKP-Cologne(b) (FET_IF1320)

IKP-Cologne(Miniball - FET_IF1320)

Sensitivity( mV / MeV)

~ 100 mV/MeV

( differential )

~ 100 mV/MeV

( differential )

~ 175 mV/MeV

( single ended )

Resolution(Cd= 0pF; cold FET) ~ 600 eV ~ 600 eV ~ 600 eV

Slope( + eV/ pF) [Cd]

< 10 eV / pF

(cold FET)< 10 eV / pF (cold FET)

< 10 eV / pF (cold FET)

Rise time *)(Cd= 0pF); *[Amplit.]

< 12 ns ( warm FET)

~ 15 ns

( cold FET)

~ 15 ns

( cold FET)

Slope( + ns/ pF) [Cd]

~ 0.25 ns

( ~ 23 ns / 45 pF )

~ 0.25 ns( ~ 26.5 ns / 45 pF )

~ 0.3 ns( ~ 25 ns / 33 pF )

U(out) @ [100 Ohm] / Power [mW]

~ 2.0V*/ ~290 mW(LM-6171; *AD-8057)

~ 2.0V*/~ 290 mW(AD-8057; LMV-6723)

~ 4.5V*/~ 450 mW ( + /- 12V) (LM-6172)

Saturation of

the 1st stage @

equiv. ~ 90 MeV (@ ~20 mW_ jFET)

equiv. ~100 MeV (@ ~60mW_ jFET)

equiv. ~100 MeV(@ ~60mW_ jFET)

Open Loop Gain > 80,000 ~ 20,000 ~ 20,000

One-wire test pulse for all segmentsOne-wire test pulse for all segments

From From anan idea available in literature idea available in literature

1 . 8

H V

P u l s e r s i g n a l

W a r m p a r tC o l d p a r t

C o r e p r e a m p l i f i e r + p u l s e r C o r e p r e a m p l i f i e r + p u l s e r

4 7

C o l d p a r t W a r m p a r t

S e g m e n t p r e a m p l i f i e r S e g m e n t p r e a m p l i f i e r

H P G e c r y s t a l ( 3 6 + 1 s e g m e n t s ) H P G e c r y s t a l ( 3 6 + 1 s e g m e n t s )

9 c m

A.Pullia, presented at AGATA week, GSI, Feb.2005

also: “Test of a new low-noise preamplifier with the MARS segmented detector and extraction of physical data from the noise measurements” presented at EDAQ meeting, Padova, Sept. 19-20, 2002

Advantage - Disadvantage

• PTFE Coaxial Cable (0.9mm)

Pulser

Pulser Resolution in Core ( < 1.5 keV @ tr ~ 30-35 ns )

Rectangular

Exponential

- Signal & Pulser same P/Z adj.

- DC level

- good DC levelat low count. rates

Signal & Pulserdifferent P/Z

* Pulser return ground signal 0 to 40 mA

Pulser block diagram

Rectangular or Exponential form

Attenuation 0 to 40 dB

•Pulser @ GND_1 (!)•Core & Segments @GND_0

Problems: twisted Core Signal_GND? - Segments return GND ?! - GND one_both ends ?! thermal shunt limitations pulser wirering, return GND (very important up to 40 mA !)

Connector problems: - only MicroMatch(20)? - formerly also MDR-26?

we badly need a test Cryostat ! ( HP-Ge Detector thermal stress)

- GND_0 Cold part- GND_1 Warm Part

Triple Cryostat Wirering_Grounding

D1 D2 D3CB CB

CS CF

RF

CF CF

RF RF

CD

CS

CC

VACUUM

x36 x3 x36

1.8Ω

cold part

6x TRIPLE CORE + PULSER 6x TRIPLESEGMENTS SEGMENTS

Ro [GND0 <-> GND1]

Al

GND_1

GND_1

~8cm~8cm

GND0

GND_0

GND_1

MDR(26)

PTFE ~8cm

~12-15cm~12-15cm

MDR(26)MDR(26) GND_1

GND_1

~8cm~8cm

MicroMatch (20)

MicroMatch (18)MicroMatch (18) MicroMatch (18)

MicroMatch (20) MicroMatch (20)

LN2 - DEWAR Al

CTT Feed through

- Superposition of individual , time dependent, Core_Return_GND_Signals

Strong crosstalk due to BLR effect if the R( GND_0 GND_1)

Cluster of three detector –and the related GND_ing problem

• Common Core_GND (cold_warm?)• Individual GND_0 (cold)• Resistance between GND_0 GND_1

Very Fast Pulser (TEK type PG-502; tr ~ 1ns)

• Pulser rise time tr~ 1ns / 50 Ohm

• Core / Segment fastest transfer function

• Overshoots ~ 20-40 % (but adjusted on bench for NO overshoot !)

FAST PULSER ( tr ~ 10, 50 ns )

Pulser tr ~ 50 ns Pulser tr ~ 10 ns

• tr segments ~ 25 ns @ ~15-20 pF• tr core ~ 29 ns @ ~ 45 pF

• we have to understand the equivalent “transfer function” of the pulser signals for core and segments !

core

segment

core

segment

•Both core and segments preamplifiers bench adjusted for fastest transfer function with no ringing for pulser signals with tr > 10 ns and/or for core_pulser tr > 65 ns

High Precision Slow Pulser Pulser PB-4 ( tr ~ 100; 250 ns)

Pulser tr ~ 100 ns

Pulser tr ~ 100 ns

Pulser tr ~ 100 ns

Pulser tr ~ 100 ns

Pulser tr ~ 250 ns

Pulser tr ~ 250 ns

Triple with Det. & twisted core. Triple with Det. & twisted core

No twisted core No twisted core

core core

corecore

segment

segment segment

segment

Uncorrected

for individual Gain

Gain corrected

Pulser Core /Segments Ratio

R ~ (40-75)

Distribution of the real Segment Preamplifiers Gain (cold + warm)

Gain Gr (A)

Gain Gr (B)

Gain Gr (C)

Gain Gr (D)

Gain Gr (E)

Gain Gr (F)

120,50 107,00 100,50 115,00 114,60 119,00

110,00 113,50 120,00 97,00 123,00 104,50

120,50 109,00 102,00 109,00 113,30 105,00

111,00 111,00 102,00 100,00 103,40 109,00

113,00 112,00 111,00 108,00 114,00 106,00

111,50 107,50 117,00 106,00 87,50 97,20

• N.B. a) but with a distribution of the warm preamplifier gain of < +/- 2 % !

b) to reduce the influence of feedback capacitor a new design of cold

part is mandatory ( … silica substrate could be a very good candidate but it’ll bring additional technological problems !)

Recovery from core saturation versus SHDW command

• Recovery time in < 2 us after INH.

• Saturation @ ~ 100MeV (equivalent gamma)

SHD_C OFF

SHD_C ON

SHD_C ON

SHD_C ON

Maximum “Dead Time”

• SHD_C OFF ~ 45 µs• SHD_C ON ~ 12.8 µs

Amplitude to Time Converter Core “Saturated “ Pulses

Pulser Segment Core (Large Signals)

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Pulser Preset (digital numbers)

U-S

egm

ent

[mV

/ 5

0 O

hm

]

0

2

4

6

8

10

12

14

16

18

20

Co

re_F

ast

Res

et D

elay

[µ

s]

Active Reset _”Saturated “ Core

- ‘Amplitude to Time Converter’ for saturated core pulses and- Non saturated Segment pulses

Core_Pulser Programmable Attenuation

• Coarse Attenuation in four steps of 10 dB (0; 10; 20; 30; 40 )

Attn 40 dB

0

0,5

1

1,5

2

2,5

10100

Attenuation (log) [dB]

Co

re

[V

]

0

10

20

30

40

50

60

70

80

90

100

Seg

men

t

[m

V]

Attn 20 dB

Linear Amplitude to Time conversion of the “saturated” reset pulses

• “VIP“ signals (~ 12 – 25 MeV)

• linearity < 2%• resolution < 1%*

* see also A.Pullia, F.Zocca

“Saturated” Pulses Linear Amplitude-Time converter

• “VIP“ signals (~ 30 – 100 MeV)

• linearity < 2%• resolution < 1%

•F. Zocca, A new low-noise preamplifier for gamma ray sensors with smart device for large signal management.Laurea Degree Thesis, Univ. of Milan, 2004

Core baseline deterioration at very large signals

Core baseline deterioration at very large signals

versus pulser mode of operation:

a) exponential ( decay time 100µs)– a(1) @ ~ 15 MeV;

– a(2) @ ~90 MeV

b) rectangular @ ~ 90 MeV

a(2)a(1)

b)

Core Rise Time versus I(D), C(v)

50

60

70

80

90

100

110

0 5 10 15 20 25 30 35

20

25

30

35

40

45

6 7 8 9 10 11 12 13

C(v) [pF]

Ris

e T

ime

[n

s]

Core Rise Time / C(v) (*)

Ris

e T

ime

[n

s]

Core Rise Time / I(Drain)

(*) Pulser PB-4 (BNC) @ 50ns rise timeI (Drain) [mA]

Segment Ringing versus Core Bandwidth (a) Fast core rise time range• Core_Pulser constant tr ~30ns• Core rise time range tr: 30-60 ns

tr ~ 32 ns tr ~ 38 ns

tr ~ 46 ns tr ~ 60.5 ns

Segment Ringing versus Core Bandwidth (b) Slow core rise time range• PB4_Pulser (tr ~ 50 ns)• Core rise time tr: 60-100 ns

tr ~ 62 ns

tr ~ 76.5 ns

Tr~ 32ns

tr ~ 72 ns

tr ~ 98 ns

Segments Overshoot / Core Rise Time

-10

-5

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120

Core Rise Time [ns]

Sem

nets

Ove

rsho

ot [

%]

Reihe1

Polynomisch (Reihe1)

Segment Overshoot versus Core Rise Time

• Unexpected dependence between core rise time (not only pulser rise time) and segments overshoot

• (to understand that see also cableling details on pag. 5–7 i.e. core return ground signal)

Rise Time versus Amplitude

• LM 6171 data sheets ( +/- 12V )

• tr ~ 28 ns @ 50 mV 24 ns @ 1000 mV

(terminated @ R=100 Ohm)

Alternatives :

• AD8057 (Volt. Feedback) ( +/- 6V only ) < 1.5 ns

• LMH6723 (Current Feedback)

( +/- 6V only ) < 1.5 ns

LM6171

AD8057

( I quiescent ~ 3 mA )

( I quiescent ~ 6 mA )

Intrinsic Pulser Resolution ( < 1keV @ tr ~30 ns )

122 keV

136 keV

Pulser

X- Pb

• Intrinsic Core_Pulser resolution measuredat different segments

< 900 eV !• Equivalent energy range in segments: ~ 10 keV- 3 MeV !

57

Co

Intrinsec Pulser Resolution ( < 1keV @ tr ~30 ns )

Co 60

57Co Pulser (Rectangular)(equiv. ~3.3MeV)

• Highest Pulser Amplitude in segments ~ 3.3 MeV (equivalent gamma) ( in Core saturated @ ~100 MeV respectively)

Pulser Resolution in Core ( < 1.5 keV @ tr ~30 ns )

1173 keV

1332keV

Pulser (+)

122 keV

136 keV

X_Pb

Pulser Mode

• Pulser Exponential Pulseform (decay time 100µs) (+) normal (-) supressed 20:1

Pulser(-)

X_Pb

Pulser(-)

122 keV

136 keV

1173 keVPulser

(+) 1332keV

Intrinsic Core resolution in AGATA Triple Cryostat (01)

• with NO Pulser 1.3 keV• with Pulser ON 1.5 keV

Structure of Core Resolutionin Coincidence with Segments Rings

1 2 3 4 5 6

Peak

Position (1332,...) keV

.285

keV

.166

keV

.353

keV

.535

keV

.543

keV

.495

keV

Resolution

FWHM

( keV )2.37 2.38 2.27 2.22 2.24 2.34

Nigel Warr, “AGATA core resolution with gate on segment

Cryostat Wirering_Cableling

• Segments: - two detectors self made “flat band” cable, one individual Cu(Be) wires - one GND_0 / detector, no twisted cable• Core: - twisted cable for D and FB signals at GND_0 (in the case of only one detector), - if all three detectors at common GND then large crosstalk (due to the superposition of Return_GND(i) signals) - Core return GND on the segments cold motherboard!• Pulser: - Pulser coaxial PTFE, 0.9 mm external diameter with individual GND_1• Warm Core_CSP: - common GND for Pulser & CSP > most probable has to be changed ?! - on board separation between A_GND and D_GND, but only one GND to the F_ADCs (as decided by Infrastructure Group, Feb. 2005) - differential outputs, with the same polarity as Segments, as well as the INH_C and SHD_C signals functionality identical to the INH_A(B) and SHD_A(B), respectively.

• Triple Cryostat Wirering: - has to be decided, as soon as possible !

Conclusions

• Test demonstrated that a pulser with a very good energy resolution (< 1keV @ segments , < 1.5keV @

core) with a rather good very long time stability and fast rise time (< 35 ns) can be obtained,

• Further developments of core_pulser assembly is mandatory (to reduce the core CSP noise with pulser ,

to optimize pulser rise time if “in situ” transfer function measurements are foreseen),

• Solution to improve the wirering in the triple cryostat have been presented by A.Pullia at the AGATA week, Strasbourg, Nov. 2005 (next two slides),

(milestones for the above mentioned tasks has to be decided)

A.Pullia, AGATA week, Nov. 2005

A.Pullia, AGATA week, Nov.2005

Position of cold preamps for nearest neighbours event

D. Weisshaar et al. AGATA Week, GSI, Feb. 2005

Crosstalk Core versus Segment Open Loop Gain

B. Bruyneel – PhD Thesis , IKP-Cologne, 2006

Acore constant at 80000

0,9988

0,999

0,9992

0,9994

0,9996

0,9998

1

1,0002

0 10 20 30 40

Seg Aseg = 80000

Seg Aseg = 20000

Seg Aseg = 10000

Seg Aseg = 5000

Core Aseg = 80000

Core Aseg = 20000

Core Aseg = 10000

Core Aseg = 5000

Crosstalk Segments versus Core_Open Loop Gain

Aseg is constant at 10000

0,9986

0,9988

0,999

0,9992

0,9994

0,9996

0,9998

1

1,0002

0 10 20 30 40

Seg, Acore = 80000

Seg, Acore =20000

Seg, Acore =10000

Seg, Acore = 5000

Core, Acore = 80000

Core, Acore = 20000

Core, Acore = 10000

Core, Acore = 5000

B. Bruyneel – PhD Thesis , IKP-Cologne, 2006