Studies on Module 0 HAC

Studies on Module 0 HAC

V. Fascianelli,V. Kozhuharov,

M. Martini,T. Spadaro,D. Tagnani

Photon veto meeting - Liverpool 2

Outline

• Reminder: HAC insertion in NA62: why/how• Module 0 HAC tests at BTF@LNF, for:– obtaining order-zero measurement of light yield– assessing possible FEE readout schemes

• First data/MC comparison studies:– simple digitization/reconstruction algorithms

implemented, following FEE scheme assumed

8/27/13


HAC: why, how• From the work by Ruggiero (23/5/2012) and Spasimir

(06/02/2013):– need a new detector to reject O(10) residual background events from K-

>p+p+p- / year– events with p- lost (due to nuclear interaction), and a p+ escaping

detection through the hole, grazing the pipe, emerging at various depths in the range 247 < z < 255 m

– need to efficiently veto p of ~40 GeV, with a detector at z = 253.35 m, while sustaining a muon halo rate of ~4 MHz (dominated by p+ m+ decays downstream GTK3)

– bad energy resolution expected due to lateral leakage– total rate reduced by x10 if E>100 MeV is required– O(<1ns) time resolution to correctly match HAC information with the

rest of event

8/27/13


HAC: why, how• A single HAC channel collects light from 6 scintillator tiles (4 mm wide)

alternating to 16-mm Pb layers• Lights from each scintillator collected by a green-centered 1-mm2 WLS fibers • Tentative detector setup: 9 modules, each with 10 channels along the

longitudinal direction

8/27/13

From F. Hahn


RO: order of magnitude cost estimate

Consider 90 channels in totalSiPM case:• 100 E/SiPM, 150 E / amplifier + Voltage bias electronics

(evaluation scaling from CHANTI board, 4000 E/32 ch’s): 22500 E

• Digitizer (GANDALF, 12 bit 500 MS/s): 60000 E for 96 channels• Grand total: 82 500 EPMT case:• 400 E/PMT, 200 E/HV-ch: 54000 E• The GANDALF is a common solution for both setups• Grand total is 115 000 E

8/27/13


HAC studies

• Order-0 questions: is the scintillator performance still valid and is the light collection enough?

• Order-1 questions: can it be instrumented with SiPM’s or we have to consider PMT’s?

• Order-2 question: can it be readout with Flash ADC’s?

8/27/13


Measurement of HAC response ratesOrder-0 questions: are the scintillator performance and the light collection still OK?• Data taken with SiPM at nominal bias voltage• Trigger set at ~30 mV (~7 photoelectrons), rates in dark of ~20 Hz • Use a Cs137, 0.18 MBq, 30.07 years radioactive source• Study trigger rates as the source is moved along the longitudinal direction

8/27/13


Measurement of HAC response rates

Order-0 questions: are the scintillator performance and the light collection still OK?• Measurement from each position repeated 4 times• Expect spacing of 4 + 16 mm, OK• 6 peaks spotted, rates span a range of x3... need cosmic-ray characterization, to

be done

8/27/13

no source

Counts from channel 3 / 10 s

Longitudinal Position (cm)


BTF runs

• Trigger setup with two positive signals from scintillator paddles

• Electron beam, 50 Hz, O(1) electron multiplicity• Readout via Flash ADC, CAEN module V1751, 8 ch’s, 10 bit, 1

GS/s:– from signal shape, evaluate maximal voltages, integrated charge

around the maximum, event-by-event pedestal, time of the maximum

• HAC runs: 570-MeV beam impact head-on onto channel 0 region at the center

• Expect some lateral leakage due to beam angular dispersion: the HAC is placed ~ 1 m downstream the pipe end

8/27/13


BTF runs: e- beam multiplicity, Q’s

8/27/13

Integrated Charge horizontal paddle (C)

Integrated Charge vertical paddle (C)-- 0 electrons-- 1 electron-- 2 electrons-- 3 electrons


BTF runs: e- beam multiplicity

Poisson distribution fit: m = 0.94(1), c2 = 1.8/1

8/27/13


HAC readout• Interface 6+1 (for calibration) fiber bundle at module end with

3x3 mm2 prototypal high-density SiPM, Hamamatsu MPPC 15 mm x15 mm pixels:– Gain of 2.5 105, at 69.3 V bias at room termperature– 57,600 15 x 15 mm2 pixels in 3x3 mm2 active area– ~ 370 pF capacitance– Gain lower than available SiPM’s by ~x3, but better time resolution

expected, since novel corrections due to delay for far pixels are present (TSV, Through Silicon Via, no wire bonding, see http://kicp-workshops.uchicago.edu/ieu2013/depot/talk-ghassemi-ardavan__1.pdf)

• Voltage supply and amplification during run with electronics tuned for a 70 pF SiPM: time performance not reliable

• Runs were acquired with a PMT readout, as well8/27/13


HAC response: sampling a signal

8/27/13

Signal amplitude [mV]

Signal amplitude [mV]

Time [ns]

SiPM readout

PMT readout


HAC response: maximal amplitude

8/27/13

Amplitude (mV)

-- 0 electrons-- 1 electron-- 2 electrons-- 3 electrons


HAC Response: charge

8/27/13

-- 1 electron-- 2 electrons-- 3 electrons

Integrated charge (C)


HAC Response: maximum amplitude

8/27/13

s(V)/V

<V> [mV]

Nominal impact energy (MeV)


HAC Response: charge

8/27/13

s(Q)/Q

<Q> [C]

Nominal impact energy (MeV)

s(E)/E ~ 35%/Sqrt(E[GeV])


SiPM characterization in dark• SiPM signals sampled in laboratory at fixed temperature and with no input

source• FEE electronics adapted from project developed for Mu2e (Martini, Tagnani,

Corradi) performing accurate APD preamplification• FEE electronics providing x97, while being matched to the SiPM capacitance

– The value correspond to optimal matching and lowest noise• Bias voltage provided via linear power supply• Study of the V-I characteristics

8/27/13

Bias voltage (V)

Current (mA)

Vop


SiPM characterization in dark• Apply a 3 mV threshold, corresponding to < 1 pe (see after)• Use oscilloscope as a Flash ADC• Sampling frequency, 1 sample every 0.4 ns

8/27/13

~8 ns rise time

~20 ns fall time

pedestal evaluation region

FADC channel # = T [0.4 ns]


SiPM in dark: the analog signal

8/27/13

Vbias = 71.4 V

Amplitude (10 mV / division)

Trigger

Time (10 ns / division)


SiPM characterization in dark• Evaluate maximum of SiPM signals and the related population• Fit the first 3 peaks, corresponding to n, n+1, n+2 photoelectrons• Perform a single fit allowing the peak-to-peak distance as free

parameter

8/27/13

Repeat the above steps in a wide range of voltage bias: 69.3 V (nominal + 0.3V) 71.8 V


SiPM characterization in dark• Change of the single-photoelectron voltage with the bias, as expected• Single photoelectron ranges from 4.5 mV to 8.5 mV as Vbias varies from

69.3 to 71.8 V

8/27/13

peak to peak distance (V)

bias voltage (V)


SiPM characterization in dark• Change of the single-photoelectron voltage with the bias, as expected• Single photoelectron ranges from 4.5 mV to 8.5 mV as Vbias varies from 69.3 to

71.8 V• Result confirmed by the position of the first peak

8/27/13

position of first peak (V)

bias voltage (V)


SiPM characterization in dark• Change of the poissonian probability, ranging from ~0.2 to ~0.6 as the bias

voltage varies• Probably an effect linked to PDE variation

8/27/13

bias voltage (V)


SiPM characterization in dark• Evaluate charge of SiPM signals and the related population• Fit the first 3 peaks, corresponding to n, n+1, n+2 photoelectrons• Perform a single fit allowing the peak-to-peak distance as free parameter• Repeat the above steps in the bias range: 69.3 V (nominal + 0.3V) 71.8 V

8/27/13Charge (pC)


SiPM characterization in dark• Gain evaulation within the expectation: 105 2 105, after correcting for

the FEE amplification of 100 (actually 97)

• Position of 1st peak confirms that the distribution is due to 1, 2, 3 photoelectrons

8/27/13

bias voltage (V)

Gain = 105

Gain = 1.8 105


MC HAC Digitization

• Complement the MC made by Spasimir with digitization and reconstruction

• The following assumptions are used:– Scintillator produces 104 photons / MeV– 10-3 of the produced photons reach the SiPM– SiPM PDE = 0.6– The SiPM Gain is 106 (it will be changed in future)– With a FEE electronics amplification of 10, a single

photo-electron produces a 4-mV peak with a 8 ns rise time and a 20 ns fall time

8/27/13


HAC MC: energy release

8/27/13

s(E)/E

<E> [MeV]

Electron energy (MeV)

electrons head-on impact


HAC MC: electrons MC reconstructed

8/27/13

s(V)/V

<V> [mV]

Electron energy (MeV)

electrons head-on impact


HAC Data/MC comparison: electrons data

8/27/13

-- Data-- MC reco-- MC truth

Fractional resolution

Electron energy


Conclusions

8/27/13

Experience with HAC basically shows a working detector:• Satisfactory operation with electron beam at Frascati BTF• SiPM characterization in dark in agreement with Hamamatsu specifications• Benefiting of previous work by Spasimir on MC, a simple procedure for

digitization/reconstruction added (at the moment the code is kept private)• Good linearity of energy response observed• Agreement between data and MC after digitization has to be proved with cosmic rays:

data with 2-3 electrons probably affected by lateral leakageSiPM operation + Flash ADC readout satisfactoryTo-do list:• improved description of MC digitization (pileup of scintillator signals)• Complete development of the low-noise voltage regulator• cosmic ray tests and additional acquisitions with radioactive source• test of final electronics (at the moment, in production)• Channel by channel intercalibration studies• Final design of readout on-board electronics and mechanical interface

Documents

Studies on Module 0 HAC