Alternatives to CsI(Tl)O. Tengblad/T. Nilsson

• Phoswich solutions• GEANT-4 simulations• Read-out electronics• Multiplexing• Swedish plans (Chalmers/KTH)

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Olof Tengblad

Developments for calorimeter of R3B@FAIR

The work carried out up to now by the groups of Santiago and Madrid have permitted to divide the calorimetro CALIFA in two parts that will have different technical solutions: a cylindrical “Barrel” around the central zone and a second solution for the forward end cup (8 – 450).

Our contribution to the design of the calorimeter has been based in a novel solution using crystals of new generation and detectors formed by two layers of crystals (Phoswich).

The task of the IEM group is thus concentrated on the forward cup Proton & detection Phoswich Electronic readout

Discussed by I. Duran

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Olof Tengblad

Protons:Using two E-detectors one can determine the full proton energy with a resolution of <5%.

Gammas: Second detector placed to solve the ambiguity on the signal

Phoswich: p- Energy resolution

E

Ep= 200MeV 20 mm LaBr E = 31 ± 1 MeV

200±10MeV(E/E=5%)

E =f( E1 ) + g( E2 )

Ep= 200MeV 30mm LYSO E = 67.5±1.8 MeV

200±7MeV(E/E=3.5%)

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Olof Tengblad

Phoswich and gamma detection

1. Simulations show that the probability of some interaction in first layer is very high, up to 80%

2. Simulations also show that the fraction of energy absorbed in 5 cm of LYSO is > 80%

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Olof Tengblad

Phoswich conclusion

To obtain the optimum situation for both protons and gammas;

First crystal layer relatively thick and of a material with excellent gamma resolution,

LaBr3(Ce) of 30 mm = 380nm decay time= 16ns =5,3 g/cm3

E/E=3%

Second crystal layer Solution 1: Optical compatible materials & single readout

Second crystal layer of a material emitting at shorter wavelength and with a different decay constant in order to separate the signals and that the second detector is transparent to the first.

LaCl3(Ce) of 150 mm = 350nm decay time= 28ns =3,8 g/cm3

E/E=5,5%

Solution 2: Double readout Second crystal of a dense, non-hygroscopic material of worse

resolution LYSO of 60 mm = 420nm decay time= 40ns =7 g/cm3 E/E=7%

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Olof Tengblad

LaBr3LYSO

30 50 mm

LaBr3 LaCl3

30 50 mm

Phoswich Solutions to be tested

Two crystals of different materials with a unique readout system? Optically compatible

EE1 E2

E

E1 E2

Two crystals of different materials but with separate readout system?

Ordered, awaiting delivery from Saint- Gobain (august 2007)

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Olof Tengblad

Ongoing Monte Carlo Simulations @ IEM to build a Phoswich prototype

MCNP (Monte Carlo N-Particle ) Code

_ crystals: LaBr3, LaCl3and LYSO_ dimensions of the crystals:

x= 10/15mm, y= 10/15mm, z= 20/30mm for LaBr3, 30/60mm for LaCl3 or LYSO

_ Ei(photons)= 5, 10, 25, and 30 MeV Ei(protons)= 10, 50 and 100 MeV_ source to detectors distances= 25, 30, 35 and 40cm _ crystals separated by teflon

GEANT4 Code

Crystal 1 Crystal 2

x

y

zp+,

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Olof Tengblad

GEANT-4 simulations – preliminary (M. Turrion

-> No gain in efficiency beyond 15 cm thickness

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Olof Tengblad

E stage 1 µmE stage 400 ± 15 µm

EURONS-DLEP: developments of detectors & readout electronics

64 detector elements á 7 mm2

128 readout channels The Solid Angle is 20% of the DSSSD

but needs 4 times more electronic-channels!

256 detector elements á 9 mm2

32 readout channels

Novel thin window design for large-area Si strip detectorTengblad et.al. Nucl. Instr. Meth A525 (2004) 458

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Olof Tengblad

MTM16: 16ch PreAmp, Shaper, Discriminator Charge sensitive PA, variable gain and polarity Timing filter & discriminator Spectroscopy amplifier Readout sequential or Zero sup. 16 boards = 256 channels to one readout bus All setting individual and Remote Controlled Low power consumption can be operated in vacuum

EURONS-DLEP development together with Mesytec chained multiplexing, spectroscopy quality: MTM16+MDI-2

32 x 16ch cards = 512ch multiplexed to

2 readout busses into 12 bit ADC

Needs some extra development to adjust to LAPDs,

and to implement Pulse Shape Identification for the

Phoswich solution

Estimated final cost of complete readout 70 €/ch

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Olof Tengblad

What to do: Multiplexed readout system.

More and more experiments in nuclear physics require more amplifier channels, filterstages and ADCs providing high signal quality are needed at lower cost per channel.

The most effective approach to reduce costs is early multiplexing within a front end electronics which is situated near the detector. From analogue signal processing requirements, the earliest stage for time multiplexing is directly behind the shaping amplifiers.

One method of time multiplexing is to store the individual amplitudes as a charge in a capacitor, switch it to a bus line one channel after the other and digitize it with an ADC in aCAMAC or VME module. Several 100 channels can be digitized this way with a minimumof cabling and only one ADC.

The proposal described here implements a simple time multiplexing with a zero suppression mode to overcome the long conversion time. In zero suppression mode not only the amplitude but also an address of the responding channels are transmitted. The implemented preamplifiers are of low power consumption for vacuum operation.

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Olof Tengblad

MTM16 - MDI2 chained multiplexing, spectroscopy quality

MTM16: 16ch PreAmp, Shaper, Discriminator Charge sensitive PA, variable gain and polarity Timing filter & discriminator Spectroscopy amplifier Readout sequential or Zero suppressed 16 boards = 256 channels to one readout bus All setting individual and Remote Controlled Low power consumption can be operated in vacuum

The trigger signal from MTM16 is well suitedas a high resolution timing signal.

The MDI2 provides two TDC channels

About 500 ns after the "gate" signal, theMDI2-sequencer is started and produces theclock sequence for reading out the MTM16.

The incoming analog amplitude data are digitizedby a 12 bit sliding scale ADC If above threshold, stored together with the ch address in a memory (fifo).After conversion ready the data can be accessedvia VME bus.

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Olof Tengblad

MDI-2 VME sequencer and ADC

High quality 12 bit (4k) conversion with sliding scale ADC (DNL < 1%).

• 10 M samples / s per bus. • Up to 512 channels can be converted

• Multi event buffer • Zero supression with individual thresholds • Supports different types of time stamping • Connected frontend modules can be remote

controled (gain, threshold, polarity).

• Address modes: A24 / A32 • Data transfer modes: D16,32,64, BLT32, MBLT64, CBLT

• Multicast for event reset and timestamping start.

Swedish plans (Chalmers/KTH)

• The KTH and Chalmers groups will initially jointly focus on investigating novel scintillation materials such as LaBr3 and LaCl3. First prototypes have already been purchased by Chalmers and are being tested at CSIC.

• The KTH group concentrates on investigating an alternative optical readout of such scintillators using the new silicon photomultiplier technology (SiPM)

• The Chalmers group will concentrate on investigating dual-layer scintillator solutions and signal processing prototypes for wavelength-differentiated read-out.

• FLUKA simulations of demonstrator etc.? (M. Lantz, Chalmers)

• Both groups plan in-beam tests, e.g. using charged particles at TSL and tagged photons at MAX-Lab, in conjunction with the other calorimeter activities within SFAIR.