Cha ac e isa ion o highly
i adia ed 3D ench silicon pixel
senso s o 4D acking wi h 10ps
iming accu acy
F. Bo ga o
1
,
2
, A. Ca dini
3
, G. M. Cossu
3
, G. F. Dalla Be a
4
,
5
,
M. Ga au
3
,
6
, L. La Del a
3
, A. Lai
3
, A. Lampis
3
,
6
*, A. Loi
3
,
M. M. Obe ino
7
,
8
, G. Simi
1
,
2
and S. Vecchi
9
*
1
Is i u o Nazionale di Fisica Nuclea e (INFN), Sezione di Pado a, Pado a, I aly,
2
Dipa imen o di Fisica,
Uni e si à di Pado a, Pado a, I aly,
3
Is i u o Nazionale di Fisica Nuclea e (INFN), Sezione di Caglia i,
Caglia i, I aly,
4
TIFPA Is i u o Nazionale di Fisica Nuclea e (INFN), T en o, I aly,
5
Dipa imen o di
Ingegne ia Indus iale, Uni e si à di T en o, T en o, I aly,
6
Dipa imen o di Fisica, Uni e si à di Caglia i,
Caglia i, I aly,
7
Is i u o Nazionale di Fisica Nuclea e (INFN), Sezione di To ino, To ino, I aly,
8
Dipa imen o
di Scienze del Fa maco, Uni e si à del Piemon e O ien ale, No a a, I aly,
9
Is i u o Nazionale di Fisica
Nuclea e (INFN), Sezione di Fe a a, Fe a a, I aly
3D ench silicon pixel senso s, ecen ly de eloped by he TimeSPOT collabo a ion,
ha e shown excellen pe o mance in e ms o spa ial esolu ion, iming p ecision
and de ec ion e ficiency. The combina ion o hese h ee ea u es make hem one
o he bes candida e o inne acking de ec o s ope a ing in high luminosi y
had on collide s expe imen s. This a icle p esen s sys ema ic cha ac e isa ions o
hese de ices made wi h minimum ionising pa icles on i adia ed senso s wi h
neu ons up o 2.5 ·10
16
1 MeV n
eq
cm
−2
. The esul s show ha 3D ench pixels
ha e ex emely high esis ance o adia ion. The measu ed ime esolu ion and he
de ec ion e ficiency o i adia ed senso s ma ch hose o non-i adia ed ones i a
sligh ly highe bias ol age, ew ens o Vol s, is applied o he pixels. As o oday, 3D
ench pixels a e he only senso s capable o achie ing 10 ps ime esolu ion a e
being i adia ed a ex emely high fluences, ex ending by a he capabili ies o
u u e acking sys ems o HEP expe imen s ope a ing unde ex eme condi ions.
KEYWORDS
pa icle acking de ec o s, solid-s a e de ec o s, iming de ec o s, adia ion-ha d
de ec o s, adia ion ha dness, high ime esolu ion, high luminosi y
1 In oduc ion
Fu u e high ene gy physics expe imen s a had onic collide s o esee ope a ing a an
inc eased ins an aneous luminosi y, significan ly la ge (O(10)) han he cu en alues. As
a consequence he occupancy o acking de ec o s will inc ease, a ec ing he acking and
he e ex econs uc ion e ficiencies and he o e all e en econs uc ion capabili y.
Fu he mo e, he de ec o s will ace highe le els o adia ion fluences, equi ing supe io
adia ion ha dness o gua an ee eliable pe o mance h oughou he du a ion o da a- aking pe iod.
OPEN ACCESS
EDITED BY
Gio anni Pa e nos e ,
B uno Kessle Founda ion (FBK), I aly
REVIEWED BY
Ma co Po oli,
SINTEF Digi al, No way
Gab iele Giacomini,
B ookha en Na ional Labo a o y (DOE),
Uni ed S a es
Ma cos Fe nandez Ga cia,
Spanish Na ional Resea ch Council (CSIC),
Spain
*CORRESPONDENCE
A. Lampis,
[email p o ec ed]
S. Vecchi,
[email p o ec ed]
RECEIVED 28 Feb ua y 2024
ACCEPTED 04 Ap il 2024
PUBLISHED 22 Ap il 2024
CITATION
Bo ga o F, Ca dini A, Cossu GM, Dalla Be a GF,
Ga au M, La Del a L, Lai A, Lampis A, Loi A,
Obe ino MM, Simi G and Vecchi S (2024),
Cha ac e isa ion o highly i adia ed 3D ench
silicon pixel senso s o 4D acking wi h 10 ps
iming accu acy.
F on . Phys. 12:1393019.
doi: 10.3389/ phy.2024.1393019
COPYRIGHT
© 2024 Bo ga o, Ca dini, Cossu, Dalla Be a,
Ga au, La Del a, Lai, Lampis, Loi, Obe ino, Simi
and Vecchi. This is an open-access a icle
dis ibu ed unde he e ms o he C ea i e
Commons A ibu ion License (CC BY). The use,
dis ibu ion o ep oduc ion in o he o ums is
pe mi ed, p o ided he o iginal au ho (s) and
he copy igh owne (s) a e c edi ed and ha he
o iginal publica ion in his jou nal is ci ed, in
acco dance wi h accep ed academic p ac ice.
No use, dis ibu ion o ep oduc ion is
pe mi ed which does no comply wi h hese
e ms.
F on ie s in Physics on ie sin.o g01
TYPE O iginal Resea ch
PUBLISHED 22 Ap il 2024
DOI 10.3389/ phy.2024.1393019
The ATLAS, CMS and LHCb collabo a ions ha e shown ha i
is possible o eco e he e ex econs uc ion pe o mance o he
cu en de ec o s by measu ing he ime o he acks wi h an
accu acy o he o de O(10 ps) [1–3]. In his con ex , he
TimeSPOT
1
R&D p ojec [4] has de eloped a new amily o 3D
silicon pixel senso s wi h 55 μm pi ch ha ha e shown excellen ime
esolu ion o Minimum Ionising Pa icle (MIP) de ec ion, which
make hem an ideal candida e o be used in high occupancy acking
de ec o s ope a ing close o he pa icles in e ac ion poin s.
To es he adia ion ha dness o hese senso s an i adia ion
campaign has been ca ied ou exposing se e al TimeSPOT es
s uc u es o neu ons wi h a o al i adia ion fluence up o 2.5 ·10
16
1 MeV n
eq
cm
−2
. The i adia ed 3D ench senso s ha e been hen
sys ema ically cha ac e ised wi h 180 GeV/c cha ged had ons om
he CERN SPS/H8 beamline. The iming pe o mance as well as he
de ec ion e ficiency o he i adia ed senso s ha e been e alua ed
and compa ed o hose o he non-i adia ed pixels.
2 Ma e ials and me hods
2.1 I adia ed 3D ench senso s
The TimeSPOT senso s (Figu e 1), e e ed also as 3D ench
senso s, a e silicon 3D pixels wi h he elec odes shaped in o de o
maximise he iming pe o mance o MIP de ec ion [5]. The
TimeSPOT pixel has a dimension o 55 × 55 μm
2
wi h an ac i e
hickness o 150 μm. The senso is cha ac e ised by ench shaped
elec odes: wo ex e nal ohmic-wall elec odes, which ex end o e he
en i e ow o a pixel ma ix o p o ide he bias ol age o each pixel and
a collec ing elec ode 40 × 5 μm
2
wi h a hickness o 135 μm[6].
The TimeSPOT senso s ha e been ully cha ac e ised in wo
beam es campaigns ea u ing bo h excellen ime esolu ion, o
abou 10 ps, and de ec ion e ficiency o 99% [5,7–10].
In gene al, 3D senso s a e expec ed o ha e an highe adia ion
ha dness wi h espec o plana silicon senso s due o he sho e
in e -elec odes dis ance which gua an ees a lowe apping
p obabili y o cha ge ca ie s du ing hei mo ion owa ds he
elec odes [11]. Radia ion ole ance o 3D columna senso s has
been al eady p o ed up o 3 ·10
16
1 MeV n
eq
cm
−2
[12] o wha
conce ns he cha ge ca ie collec ion e ficiency. A simila beha iou
is expec ed also o 3D ench senso s o which howe e he
adia ion ha dness was ne e es ed. To e i y he adia ion
ole ance o he TimeSPOT senso s an i adia ion campaign has
been ca ied ou a he TRIGA Ma k II Reac o
2
a he Jože S e an
Ins i u e in Ljubljana, Slo enia. Se e al es s uc u es o he second
TimeSPOT ba ch, p oduced in 2020 by Fondazione B uno Kessle
(FBK) in T en o, I aly, we e i adia ed a wo di e en neu on
i adia ion fluences o 1.0 ·10
16
1 MeV n
eq
cm
−2
and 2.5 ·10
16
1 MeV
n
eq
cm
−2
. A e i adia ion he es s uc u es we e s o ed in a
empe a u e con olled box a abou −20 °C, o p e en adia ion
damage mi iga ion due o he e e se annealing. Two ypes o es
s uc u es, he single pixel and he iple-s ip (Figu e 2), we e hen
wi e bonded o he eadou boa ds and s o ed back a −20 °C. In he
single pixel s uc u e he inne mos o se en adjacen pixels in a ow
is eadou , while he wo adjacen pixels a e connec ed o g ound, o
gua an ee he p ope elec ic field configu a ion. This s uc u e has
been used o he cha ge collec ion (ampli ude) and iming
FIGURE 1
Geome y o a 3D ench- ype silicon pixel. (A) TimeSPOT pixel ende ing wi h physical dimensions. (B) S uc u e o a senso and i s doping p ofiles
( ed o n + doping, g een o p–doping and blue o p + doping).
1h ps://web.in n.i / imespo /index.php 2h ps://www. uwien.a /en/ igacen e / iga eac o
F on ie s in Physics on ie sin.o g02
Bo ga o e al. 10.3389/ phy.2024.1393019
cha ac e iza ions. The iple-s ip s uc u e consis s o 30 pixels
placed in h ee adjacen ows which ha e he eadou elec odes
sho ed oge he . This de ice, ha ing a la ge ac i e a ea, has been
used o he e ficiency measu emen s.
The es s uc u es a e eadou h ough he TimeSPOT single
channel on -end elec onic boa ds de ailed in [13]. This ci cui
ea u es a signal- o-noise a io (S/N) o abou 20 and an
elec onic ji e below 7 ps a 2 C inpu cha ge. The powe
consump ion is abou 70 mW/channel. The boa d di ec ly
hos s he es s uc u es and p o ides he bias ol age o he
senso s by means o a conduc i e ape placed on he back side o
he es s uc u es (Figu e 3).
2.2 Tes beam se up
I adia ed TimeSPOT senso s ha e been es ed in May 2022 a
he CERN SPS/H8 beamline wi h a 180 GeV/c posi i e had ons
beam. The beam, on a e age, consis s o 10
6
pa icles which a e
ex ac ed e e y 30 s in a 4 seconds-long spill and ocused on an
app oxima ely ci cula spo o 8 mm adius measu ed a he se up
loca ion. The se up (Figu e 4) consis s o a o al o ou de ec o s
p ecisely aligned wi h espec o he beam line: wo 3D ench
senso s and wo mic ochannel-pla e pho o-mul iplie s (MCP-
PMTs). The wo 3D ench silicon senso s, along wi h hei
espec i e on -end elec onics boa ds, ha e been secu ely
ins alled wi hin an elec omagne ically shielded ligh -
igh enclosu e.
One o he senso s, he i adia ed s uc u e, is ope a ed a low
empe a u e. To do ha he senso is placed in a cold,
empe a u e-moni o ed en i onmen , which is isola ed om
he o he pa o he ligh - igh enclosu e by means o a
polys y ene box. D y ice has been egula ly filled inside wo
3D p in ed con aine s posi ioned inside he polys y ene box.
This ela i ely simple sys em e ec i ely enables he ope a ion o
he i adia ed senso s wi hin a empe a u e ange [−40, −20]°C
o abou 10 h. The senso posi ioned wi hin he polys y ene box
is fixed o a s a iona y moun which only allows o manually
o a e he senso a ound he e ical di ec ion o measu e he
senso esponse o non-no mal beam incidence. The o he
(non-i adia ed) senso is moun ed on a mo able holde
ou side o he he mally isola ed box. Such holde is d i en
by wo closed-loop piezoelec ic linea s ages, allowing
mo emen s o up o 16 mm wi h a posi ion accu acy o 10 nm
in he ans e se di ec ion ela i e o he beam line. The second
senso , moun ed on he piezoelec ic holde , p o ides a signal
o he acquisi ion igge allowing unbiased measu emen s o
he de ice unde es (DUT). Two mic ochannel-pla e pho o-
mul iplie s a e employed o he p ecise measu emen (3–4ps)
o he ime o a i al (TOA) o each pa icle. Bo h pho o-
mul iplie s ea u e a 18 mm diame e and a 5.5 mm hick
qua z inpu window.
The signals om he silicon senso s and he wo MCP-PMTs
a e p ocessed and eco ded by a 8 GHz analog bandwid h 20 GSa/s
4 channels digi al oscilloscope. The connec ion o he senso s and
he MCP-PMTs o he oscilloscope is made h ough low-loss RF
cables. The ypical igge equi es he coincidence in a ime
window o 20 ns o wo signals, one o he MCP-PMTs and one
o he non-i adia ed 3D ench senso , wi h a minimum
ampli ude. This igge condi ion a oids bias on he DUT
measu emen s, which is no in ol ed in he acquisi ion
FIGURE 2
Pic u es o some o he 3D pixel es s uc u es used in his wo k. Fo each s uc u e he ac i e a ea is ou lined in ed. (A) Single pixel senso ; (B) iple
s ip senso (30 pixels loca ed in h ee adjacen ows).
FIGURE 3
The TimeSPOT single channel boa d [14]. A magnifica ion o he
es s uc u e wi e bonded o he boa d inpu is also epo ed.
F on ie s in Physics on ie sin.o g03
Bo ga o e al. 10.3389/ phy.2024.1393019
FIGURE 4
Pic u es o he beam es se up. (A) F on iew o he ligh - igh box con aining he wo silicon senso s aligned; he i adia ed senso is placed
be ween wo d y ice con aine s used o he cooling. (B) Back iew o he wo silicon senso s in which he empe a u e senso (PT100) is isible. (C) Global
iew o he se up showing he black ligh - igh box con aining he polys i ene box, whe e he i adia ed senso is placed, and he wo MCP-PMTs
p o iding he ime o a i al o he pa icles. The oscilloscope used o he signal acquisi ion is also isible in he pic u e.
FIGURE 5
A ypical e en in which a cha ged pa icle c osses he ou de ec o s. The signals om he wo silicon senso s a e shown in yellow (non-i adia ed)
and g een (i adia ed), while he signals o he wo MCP-PMTs a e epo ed in o ange and blue.
F on ie s in Physics on ie sin.o g04
Bo ga o e al. 10.3389/ phy.2024.1393019
equi emen s. A ep esen a i e e en eco ded wi h he desc ibed
se up is epo ed in Figu e 5.
2.3 Analysis me hod
The analysis me hod s ic ly ollows wha discussed in p e ious
publica ions [5,8]. Each wa e o m is p ocessed o de e mine he
signal ampli ude and ime o a i al (TOA).
A signal is iden ified by looking o a minimum in he wa e o m
in a ime window whe e signals a e expec ed o con ibu e. The
signal ampli ude is de e mined by sub ac ing he minimum alue
ound om he co esponding ex apola ed alue o he baseline,
which is de e mined e en -by-e en by fi ing he fi s samples o
he wa e o m.
Among he di e en me hods al eady de ailed in [5,8], he
e e ence and he spline a e used in his a icle. The e e ence
me hod embodies he ampli ude and ise ime compensa ion (ARC)
FIGURE 6
Signal ampli ude dis ibu ions o 3D ench single pixels o di e en bias ol age ope a ion a i adia ion fluence o (A) 1.0 ·10
16
1 MeV n
eq
,(B) 2.5 ·
10
16
1 MeV n
eq
cm
−2
and o he (C) non-i adia ed senso .
F on ie s in Physics on ie sin.o g05
Bo ga o e al. 10.3389/ phy.2024.1393019
me hod [15]. In his app oach, he signal wa e o m unde goes a delay o
app oxima ely hal i s ise ime, ollowed by sub ac ing he delayed
wa e o m om he o iginal. Subsequen ly, he TOA is de e mined as
he ime whe e he esul ing wa e o m exceeds hal o i s maximum
ampli ude. On he o he hand, he spline me hod in e pola es he
wa e o msusingcubicsplines.TheTOAis hense o he imea
which he signal exceeds a specified ac ion (20%) o i s
maximum ampli ude.
While he e e ence me hod has shown he bes pe o mance in
e m o ime esolu ion, he spline me hod has a wide applica ion
being a efined, o -line implemen a ion o he cons an ac ion
disc imina o .
The analysis me hod u ilised is p o ed no o bias he esul s,
which is a undamen al equi emen o he measu emen s ha a e
discussed in he ollowing. In pa icula , i is capable o econs uc
he obse ables also in case o e y low cha ge deposi s, which is
FIGURE 7
(A) De ec ion e ficiency e sus he bias ol age o he i adia ed and non-i adia ed 3D ench senso s ope a ed a no mal beam incidence
condi ion. (B) De ec ion e ficiency e sus il angle o he i adia ed (0°,5
°,20
°) and non-i adia ed (0°,5
°,10
°,20
°) 3D ench senso ope a ed a a bias
ol ages o −130 V and −100 V, espec i ely.
FIGURE 8
Dis ibu ions o he di e ence be ween he ime o a i al o he 3D ench single pixel ( e e ence me hod) and he ime e e ence,
Si
−〈
MCP-PMTs
〉
o he single pixel i adia ed a (A) 1.0 ·10
16
and (B) 2.5 ·10
16
1 MeV n
eq
cm
−2
, bo h ope a ed a V
bias
=−150 V. The dis ibu ions a e fi wi h he sum o wo
Gaussian unc ions (blue dashed lines) desc ibing he signal, and a cons an ( ed dashed line) modelling he backg ound.
F on ie s in Physics on ie sin.o g06
Bo ga o e al. 10.3389/ phy.2024.1393019
impo an o he cha ac e isa ion o he pe o mance o he whole
de ec o unde es ha ypically is no pa o he igge ing logic.
3 Resul s
3.1 Single pixel signal ampli ude
Radia ion gene a es aps in he silicon bulk ha block he cha ge
ca ie s o a ime by a la ge han he ypical senso cha ge
collec ion ime. As a consequence, i adia ed senso s ea u e a
educ ion o bo h he collec ed cha ge and he signal ampli ude,
which can be mi iga ed by inc easing he bias ol age applied o he
senso . To s udy his e ec , he wo 3D ench silicon pixel s uc u es,
i adia ed a 1.0 ·10
16
and 2.5 ·10
16
1 MeV n
eq
cm
−2
, a e ope a ed a
di e en bias ol ages (−20 V, −40 V, −100 V, −120 V and −150 V).
Figu e 6 shows he esul ing ampli ude dis ibu ions which a e
compa ed o he measu emen s o he non-i adia ed pixel om [8].
Bo h i adia ed senso s ea u e a clea dependency o he mos p obable
ampli ude alue on he bias ol age. No ice ha since he amplifie
boa ds used o he wo i adia ed senso s ha e sligh ly di e en gains,
an exac quan i a i e compa ison be ween he mos p obable ampli ude
alues canno be done. Ne e heless, i is e iden ha bo h i adia ed
senso s eco e a pulse heigh dis ibu ion simila o hose o he non-
i adia ed one when a bias ol age sligh ly lowe han −100 V is applied.
Mo eo e , he ac ha he senso i adia ed a 2.5 ·10
16
1MeVn
eq
cm
−2
s ill shows a egula , Landau-shaped dis ibu ion sugges s ha he
adia ion ha dness limi o such senso s could be e en highe .
These measu emen s clea ly p o e he adia ion ha dness o
such de ices and he unchanged pe o mance wi h espec o non-
i adia ed senso s indica e ha hey can be ope a ed e en a fluences
highe han 2.5 ·10
16
1 MeV n
eq
cm
−2
.
3.2 De ec ion e ficiency
The de ec ion e ficiency o i adia ed senso s is s udied in
di e en condi ions and compa ed o he published esul s o he
non-i adia ed senso s [8]. The measu emen is pe o med using
a iple-s ip s uc u e as DUT, and by igge ing on acks
c ossing a 3D ench single pixel p ecisely cen ed,
p ojec i ely along he beam line, in on o he DUT. A
pa icle de ec ed by he igge ing pixel will also c oss he
iple s ip p oducing a signal unless i ends up inside he
enches o ge s apped in he bulk. The wo MCP-PMTs a e
also eadou o ob ain a p ecise cha ged pa icle ime e e ence.
The e ficiency is gi en by he a io η=N
s
/N
, whe e N
s
is he
numbe o e en s de ec ed by he iple-s ip senso and N
is he
FIGURE 9
Time esolu ion o he single pixels as a unc ion o he bias ol age o he di e en i adia ion fluences ob ained wi h he (A) e e ence and (B) spline
me hods. The con ibu ion due o he esolu ion o he ime e e ence is sub ac ed. I adia ed pixels a e ope a ed in a empe a u e ange [−40, −20]°C,
while non-i adia ed pixel is ope a ed a oom empe a u e.
TABLE 1 Time esolu ion o non-i adia ed and i adia ed 3D ench pixels
ope a ed a di e en il angles. The con ibu ion due o he esolu ion o
he ime e e ence is sub ac ed. The senso s we e ope a ed a a bias
ol age o −100 V.
Fluence σSi
e
( e e ence) [ps]
σSi
e (spline) [ps]
0°20°0°20°
No i adia ed 12.0 ± 0.7 17.5 ± 0.9 17.8 ± 1.0 21.7 ± 0.9
2.5 ·10
16
1 MeV n
eq
cm
−2
9.8 ± 0.4 13.5 ± 0.6 13.6 ± 1.1 16.9 ± 0.9
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Bo ga o e al. 10.3389/ phy.2024.1393019
numbe o igge s. Addi ional equi emen s on he TOA o he
signal in he DUT wi h espec o he ime e e ence gi en by he wo
MCP-PMTs as well as co ec ions due o small beam di e gence a e
applied ollowing he same me hods epo ed in [8].
Di e en measu emen s a e pe o med using he wo i adia ed
3D ench iple-s ip s uc u es: by a ying ei he he bias ol ages o
he il -angle wi h espec o he beam line. Figu e 7A shows he esul s
o he iple-s ip s uc u e i adia ed a 1.0 ·10
16
1 MeV n
eq
cm
−2
as a
unc ion o he bias ol age (g een poin s). Fo V
bias
≤−60 V he
de ec ion e ficiency is compa ible wi h he alue measu ed o he
non-i adia ed senso (black poin s). This esul is consis en wi h he
eco e y o signal ampli ude s udied in he p e ious sec ion.
Since he enches a e a non-ac i e olume, 3D ench senso s
each he ull de ec ion e ficiency only i ope a ed il ed wi h espec o
pa icle fligh di ec ions. The e o e, he de ec ion e ficiency o he iple-
s ip s uc u e i adia ed a 2.5 ·10
16
1MeVn
eq
cm
−2
is e alua ed as a
unc ion o he il angle and compa ed o he esul s ob ained o he
non-i adia ed senso [8]. The esul s epo ed in Figu e 7B show ha
he e ficiency o he i adia ed senso ( ed poin s) is compa ible wi h
ha o a non-i adia ed senso (black poin s) eaching abou 99%
de ec ion e ficiency when il ed a angles la ge han 10°. The epo ed
measu emen s a e ob ained o a bias ol age o −130 V and −100 V o
he i adia ed and non-i adia ed senso s, espec i ely.
These esul s show ha he i adia ed senso s ha e he same
beha iou o non-i adia ed ones by p o iding highe absolu e bias
ol age, in ag eemen o wha is obse ed o he ampli ude measu emen s.
3.3 Time esolu ion
Ano he key aspec o cha ac e ise he de ec ion capabili ies o
he 3D ench silicon senso in high adia ion en i onmen is gi en
by i s iming pe o mance a e i adia ion.
In his sec ion we epo he iming pe o mance o he wo 3D
ench single pixel s uc u es, i adia ed a 1.0 ·10
16
and 2.5 ·10
16
1 MeV n
eq
cm
−2
, ope a ed a di e en bias ol ages ([−150, −20]V) a
wo di e en il angles wi h espec o he beam line (0°and 20°). Fo
hese measu emen s he acquisi ion was igge ed by he coincidence
o signals de ec ed on a non-i adia ed silicon s ip senso
3
placed
ups eam he pixel and wo MCP-PMTs loca ed downs eam. The
pixel was ca e ully aligned in he beam ans e se plane wi h espec o
he s ip in o de o maximise he a e o de ec ed coincidences.
The ime o a i al o he es ed senso (
Si
) is de e mined by
means o he e e ence and spline me hods discussed in Sec ion 2.3.
The iming pe o mance o he senso a e measu ed wi h espec o
he ime e e ence gi en by he mean o he wo MCP-PMTs TOAs
(〈
MCP-PMTs
〉), which has a p ecision in he ange o 3 ps–4 ps.
Figu e 8 shows he dis ibu ions o
Si
−〈
MCP-PMTs
〉 o he wo
i adia ed pixels ope a ing a bias ol age o −150 V. Minimal
equi emen s on he ampli udes o he MCP-PMTs and on he
igge ing senso a e applied o ejec badly econs uc ed e en s.
The wo dis ibu ions a e e y simila o each o he and ha e he same
cha ac e is ics as he dis ibu ion o non-i adia ed pixels (see Figu e 9
o Re ; [8]), ea u ing a na ow peak and a small ail due o la e signals.
The dis ibu ion is fi by he sum o wo Gaussian unc ions desc ibing
he signal, and a cons an modelling he backg ound. The ime
esolu ion o he single pixel, σSi
e is ob ained by combining he
pa ame e s o he wo Gaussian unc ions and by sub ac ing he
unco ela ed con ibu ion due o he ime e e ence ji e .
Figu e 9 shows he esul ing alues o he ime esolu ion as a
unc ion o he senso bias ol age o he wo i adia ed pixels and, as a
e e ence, o he non-i adia ed one, ope a ed espec i ely a low (in he
ange [−40, −20]°C) and oom empe a u e. Bo h esul s ob ained wi h
he e e ence and he spline me hods a e epo ed. The i adia ed
senso s ha e e y simila iming pe o mance o he non-i adia ed
one. The ime esolu ion ob ained wi h he e e ence me hod a a bias
ol age o −100 V a e 9.8 ± 0.4 ps o he 2.5 ·10
16
1MeVn
eq
cm
−2
pixel
and 11.3 ± 0.7 ps o he 1.0 ·10
16
1MeVn
eq
cm
−2
pixel o be compa ed
o he 12.0 ± 0.7 ps o he non-i adia ed senso ope a ed a he same
bias ol age. These esul s clea ly show ha he ime esolu ion o 3D
ench senso is no a ec ed by he adia ion damage up o he
conside ed fluences. The sligh ly be e iming pe o mance o he
i adia ed senso s wi h espec o he non-i adia ed ones a e ela ed
o he di e en pe o mance o he on -end elec onic boa ds used o
he di e en senso s and o he di e en empe a u e condi ion. The
measu emen s also show ha he ime esolu ion o bo h he i adia ed
and non-i adia ed senso s does no imp o e significan ly below a
ce ain alue o bias ol age, which is abou −25, −60 and −80 V o he
non-i adia ed, o he 1.0 ·10
16
and 2.5 ·10
16
1MeVn
eq
cm
−2
senso s,
espec i ely. This e ec can be explained by he ampli ude dec ease o
he i adia ed senso s when ope a ed a lowe absolu e bias ol ages as
discussed in Sec. 3.1.
Gi en he con enience in ope a ing he 3D ench senso s il ed
wi h espec o he pa icle fligh di ec ions in e ms o de ec ion
e ficiency (Sec. 3.2), he ime esolu ion is also e alua ed o a il
angle o 20°.Table 1 show he esul s o bo h he non-i adia ed and
he i adia ed (2.5 ·10
16
1 MeV n
eq
cm
−2
) pixels. Bo h pixels ea u e a
simila wo sening o he ime esolu ion o maximum +40% when
ope a ed a 20°. Such beha iou is due o he la ge ac ion o acks
ha c osses adjacen pixels leading o cha ge sha ing be ween wo
pixels and hus in a educed signal ampli ude o he pixel unde es
(see de ails in [8–10]). As shown in Re . [8], in such cases he iming
pe o mance eco e s ha o he single pixel a no mal incidence by
combining he in o ma ion o he wo hi pixels wi h a
clus e ing algo i hm.
4 Discussion
The inno a i e 3D ench silicon pixel senso s, de eloped by he
TimeSPOT collabo a ion, ha e demons a ed excep ional pe o mance in
de ec ing high-ene gy cha ged pa icles, exhibi ing high de ec ion
e ficiency and p ecise iming esolu ion, as highligh ed in p e ious
wo ks [5,8]. This s udy explo es hei adia ion ole ance, showcasing
hei esis ance up o fluences o 2.5 ·10
16
1MeV n
eq
/cm
2
h ough
measu emen s conduc ed du ing a beam es campaign on
i adia ed senso s.
Due o adia ion damage, he de ec ion e ficiency o 3D ench
senso diminishes o V
bias
≥−40 V. Howe e , his educ ion is o se
by es o ing he ull e ficiency when applying a sligh ly la ge e e se
bias ol age. This obse a ion is suppo ed by he analysis o
3 A ow o en 3D ench pixels wi h he eadou elec odes
sho ed oge he .
F on ie s in Physics on ie sin.o g08
Bo ga o e al. 10.3389/ phy.2024.1393019
ampli ude dis ibu ions a a ious bias ol ages, e ealing a
dis inc i e peaking shape simila o ha o he non-i adia ed
pixel o bias ol ages sligh ly lowe han −100 V.
C ucially, he iming pe o mance o he i adia ed senso s
ma ch hose o hei non-i adia ed coun e pa s, unde sco ing
he negligible impac o adia ion damage on hese senso s.
As o oday, 3D ench- ype silicon de ec o s s and ou as he
as es adia ion-ha d cha ged-pa icles pixel senso s a ailable.
Thei p omising ea u es posi ion hem as a compelling solu ion
o u u e upg ades in he acking sys ems o nume ous High
Ene gy Physics expe imen s ha ope a e a excep ionally high
ins an aneous luminosi y.
Da a a ailabili y s a emen
The aw da a suppo ing he conclusion o his a icle will be
made a ailable by he au ho s, wi hou undue ese a ion.
Au ho con ibu ions
FB: Fo mal Analysis, In es iga ion, W i ing– e iew and edi ing.
AC: Concep ualiza ion, In es iga ion, Me hodology, W i ing– e iew
and edi ing. GMC: Concep ualiza ion, W i ing– e iew and edi ing.
GFDB: Concep ualiza ion, W i ing– e iew and edi ing. MG:
Concep ualiza ion, Fo mal Analysis, In es iga ion, Me hodology,
W i ing– e iew and edi ing. LLD: In es iga ion, Me hodology,
W i ing– e iew and edi ing. ALai: Concep ualiza ion, In es iga ion,
W i ing– e iew and edi ing. ALam: Concep ualiza ion, Fo mal
Analysis, In es iga ion, Me hodology, W i ing–o iginal d a ,
W i ing– e iew and edi ing. ALoi: Concep ualiza ion, In es iga ion,
W i ing– e iew and edi ing. MMO: In es iga ion, Fo mal Analysis,
W i ing– e iew and edi ing. GS: In es iga ion, Fo mal Analysis,
W i ing– e iew and edi ing. SV: In es iga ion, Fo mal Analysis,
W i ing–o iginal d a , W i ing– e iew and edi ing.
Funding
The au ho (s) decla e ha financial suppo was ecei ed
o he esea ch, au ho ship, and/o publica ion o his a icle.
This wo k was suppo ed by he Fi h Scien ific Commission
(CSN5) o he I alian Na ional Ins i u e o Nuclea Physics
(INFN), wi hin he P ojec TimeSPOT and by he
ATTRACT-EU ini ia i e, INSTANT p ojec . This p ojec has
ecei ed unding om he Eu opean Union’s Ho izon
2020 Resea ch and Inno a ion p og amme unde GA
no. 101004761.
Acknowledgmen s
The au ho s wish o hank he s a o No h Hall A ea a CERN
o hei help in he beam-line se up and ope a ions.
Conflic o in e es
The au ho s decla e ha he esea ch was conduc ed in he
absence o any comme cial o financial ela ionships ha could be
cons ued as a po en ial conflic o in e es .
The au ho (s) decla ed ha hey we e an edi o ial boa d
membe o F on ie s, a he ime o submission. This had no
impac on he pee e iew p ocess and he final decision.
Publishe ’s no e
All claims exp essed in his a icle a e solely hose o he au ho s
and do no necessa ily ep esen hose o hei a filia ed o ganiza ions,
o hose o he publishe , he edi o s and he e iewe s. Any p oduc
ha may be e alua ed in his a icle, o claim ha may be made by i s
manu ac u e , is no gua an eed o endo sed by he publishe .
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