1. Update on MOMENT’s Target Station Studies
Nikos Vassilopoulos, IHEP/CAS Hanjie Cai, IMP/CAS

2. Nikos-MOMENT Target Studies
Layout
MOMENT in future
Leptonic CP-violation
Decay at rest source
Pions decays neutrino beam
Description
Why a MW system
Application
Hg liquid jet
pion capture
Radiation
Future:
Granular Waterfall
Comparison with Hg-jet
R&D project
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

3. MOMENT’s high-field superconducting solenoid
Baseline design: super conductive solenoid from ~ 14 T -> 3 T
2 first Nb3Sn coils, 3 last NbTi coils
80 -> 60 cm thick W-shielding <-> 15 MW proton beam
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

4. MOMENT’s high-field superconducting solenoid
~ 1 m aperture due to collection of secondary /tertiary beams and space for inner shielding
Based on Nb3Sn superconducting conductors, CICC (Cable-in-Conduit Conductor) coil (ITER)
HTS coils are also under consideration
High-field magnet R&D efforts at IHEP (incorporated with SPPC)
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

5. π+ production and PT acceptance for adiabatic solenoids
for any adiabatic taper solenoid
B1=14 T, r1 = 20 cm
PT1 = 420 MeV/c
B2 = 3 T, r2 = 43 cm
PT2 = 193 MeV/c _
π+ for
<Eμ> ~ 300 ± 50% MeV
(<Eμ> ~ 57 % <Eπ> )
PT accepted
r1 = 20 cm, r2 = 43 cm
PT accepted
r1 = 14 cm, r2 = 30 cm
PT accepted
r1 = 7 cm, r2 = 15 cm
capture
PTmax = 3 * Bz (T) * rcs (cm) / 2 _
FLUKA 2015 (1e6 p.o.t.)
NuFact17-Sep 2017

6. Target for neutrinos and muons
Hg-jet target (similar to NF design, MERIT) as baseline
Higher beam power: heat load, radioactivity <-> 15 MW
On the other hand, easier to some extent due to CW proton beam (no shock-wave problem)
More interests in developing fluidized granular target in collaborating with C-ADS target team (why, explained later)
MERIT (2007), Hg-jet & p-24 5, 10, 15 T:
MERIT: Proof-of-principle for generating intense muon and neutrino beams from liquid Hg-jet and protons
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

7. Nikos-MOMENT Target Studies
Target evolution from conventional neutrino beams to
super beams, MOMENT, neutrino factories & muon collider
Chris Densham
or segmented
flowing types (liquids, granules…):
heat transfer: dissipate high energy densities, high total power
can be pumped away, cooled externally & recirculated, material replenish
CNGS (segmented), T2K, T2HK, nuSTORM, NOvA, LBNF/DUNE…
Super Beams: SPL, ESSnuSB
NF (?)
MOMENT, NF, Muon Collider…
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

8. Optimization of pion capture
adiabatic field analysis: slower vs fast tapers
Hg-jet target: tilt, length, radii, proton beam size
proton beam energy
W-waterfall granular target
comparisons between different Monte – Carlos (FLUKA-GEANT4)
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

9. Adiabatic field analysis: slower vs fast tapers, why does it matter ?
For an adiabatic reduced field
coil shield aperture limits maximum transverse momentum at target region
transverse momentum reduction along taper
meson beam size expansion <-> shield configuration at MCS
slower taper <-> thicker shielding
pion capture
PTmax = 3 * Bz (T) * rcs (cm) / 2
B2<B1
Adiabatic, slow field change, conservation of magnetic flux B1
helical trajectories
B x r2 = C -> r2/r1 = √B1/B2
P2T / B = C -> PT2/PT1 = √B2/B1
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

10. adiabatic field analysis
slower decrease, thicker shielding
steepest decrease, baseline
L = 5 m
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

11. particle yields for Ltaper= 5 m as function of proton Ek+
2.5 GeV
π+μ
2 GeV
1.5 GeV
selection in red
pions < P (GeV/c) < 0.776
muons < P (GeV/c) < 0.438
statistical error < 1 %
tilt
2.5 GeV
2.5 GeV
π+μ
π+μ
2 GeV
2 GeV
1.5 GeV
1.5 GeV
length
radii
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

12. particle yields for Ltaper= 50 m as function of proton Ek+
2.5 GeV μ
2 GeV
1.5 GeV
selection in red
pions < P (GeV/c) < 0.776
muons < P (GeV/c) < 0.438
statistical error < 1 %
tilt
2.5 GeV
2.5 GeV μ μ
2 GeV
2 GeV
1.5 GeV
1.5 GeV
length
radii
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

13. yields as function of tilts at 2 GeV for π+, π- & μ+, μ-
Ltaper = 5 m π+ π-
Ltaper = 50 m μ+
~75 % μ-
selection in red
pions < P (GeV/c) < 0.776
muons < P (GeV/c) < 0.438
statistical error < 1 %
~ 90 %
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

14. Hg-jet optimized parameters
FLUKA, 5, 50 m inverse Gaussian + 1st degree inverse adiabatic solenoid:
tilt 100 mrad or more
length 25 cm or more
radius 5 mm or more
Geant4beamline:
10% less yieds
similar values of target physical parameters
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

15. Radiation studies: energy deposition
energy deposition on coils and shield with FLUKA
deposited energy caused by charged particles, gammas, neutrons
total energy : 10 MW
max. volumetric heat : 100 W/cm3
energy deposition in SC below 1 kW
He or water cooling multiple channel is studied for the shield
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

16. Radiation damage: neutron flux & dpa
neutron flux per year as function of radius, length CS
dpa per year as function of radius, length CS
FLUKA
Radiation damage:
neutron flux > 1021 n / m2 / year
Damage Al or Cu-stabilizers of Nb3Sn and NbTi superconductor wire
Loss of electrical and thermal conductivity of the stabilizers and the whole coil respectively
Al-stabilizer could recover 100% by annealing
dpa > 1 per year
shield deterioration in the region surrounding the Hg-jet
Future shield optimization with slower adiabatic taper and verification with other monte-carlos
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

17. Granular waterfall as alternative flowing target @ 15 MW
Why using an alternative flowing target other than Hg-jet
toxicity -> recirculation circuit
possible technical limitations with jet velocity: needs 70 m/s to accommodate 15 MW -> questionable jet stability
high number of neutrons -> radiation damage on shield and coils (high Z)
Neutrino Factory and Muon Collider studies (US) considered Gr target for up to 1.5 MW (from 2000, nuFact15-16)
What are the advantages of a granular waterfall target over a liquid one
high flow rate, large stream cross section -> high power densities absorbed and removed
reliable, circuit simplicity -> gravity driven flow of granules
material is already broken – intrinsically damage proof
no cavitation, splashing or jets as for liquids
shock waves constrained within material grains
If the new target produces similar meson yields then is considerable.
Are the reduced and variable (effective) density and the geometry of the waterfall an obstacle to pion’s generation ?
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

18. Waterfall granular target project for MOMENT
Discrete Element Model MC at IMP, ADS & MOMENT target groups (NuFact16, “Phys.Rev.Accel.Beams 20 (2017) no.2, ”)
Toy FLUKA model (2015, NuFact16)
shows -10 % captured pions
all momenta in black
selection in red
0.22 < P (GeV/c) < 0.78
statistical error < 1 %
Hg-jet
0.077 π/p.o.t.
0.063 π/p.o.t.
toy W-waterfall model indicates that pion yields not restrained by the reduced density and geometry of the waterfall
DEM analysis indicates that the right flow rate and velocity can be achieved but effective density is not optimized in this study
granular waterfall target has the potential to be considered alternatively
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

19. Nikos-MOMENT Target Studies
Schematic of the granular waterfall target station
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

20. representation in FLUKA, 100 mrad turn, 5 m taper, W-slab with reduced densityx
downstream x z y y
upstream z x
nuFACT17
MOMENT

21. best π-yields for W-waterfall as function of densityHg
0.077 π/p.o.t.
0.063 π/p.o.t.
λW(100%) = 10 cm
all momenta in black
selection in red
pions < P (GeV/c) < 0.776
statistical error < 1 %
nuFACT17
MOMENT

22. π-yields as function of L, dW = 56 %
100 mrad turn
π+/π- = 1.86/1.
10% less pion yield than Hg-jet target Hg
0.077 π/p.o.t.
0.063 π/p.o.t.
λW = 10 cm
nuFACT17
MOMENT

23. Schematic representation of beam-target interaction for the granular waterfall target
Density distributions with different width
with DEM analysis
Density distributions

24. Nikos-MOMENT Target Studies
Different regions for the liquid mercury/powdery tungsten jet and the granular waterfall
Parameters of the beam profile and the target geometry
varies
~ 2.5 m/s
Dominant advantage of granular waterfall:
Larger mass flow for heat removing than others
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

25. Tunnel Geometry: Magnetic Field:
D0.6 x L50 m
Magnetic Field:
15T in beam-target interaction region, tapers to 4T when z > 15 m
Muon yields collected at z=50 m for different target widths and lengths:
P (GeV/c) > 0
150 < P (GeV/c) < 450

26. Nikos-MOMENT Target Studies
Comparison to Hg Jet
Produced Pions
Collected Muons
Pi Pi-
P (GeV/c) > < P (GeV/c) < 450
Hg Jet
Granular Waterfall
Muon yield: ~20% less
Averaged energy: higher
very close
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

27. Future joint-project with C-ADS working group
It will be proposed to NSFC, IHEP & IMP, March 2018):
Simulations in order to realistically achieve similar capture efficiency with Hg-jet and efficient heat transfer
Geometry
effective density
flow rate and velocity
Experiment
verification of reliability and stability of the waterfall flow
interaction with high magnetic field
test different materials
Aim to answer about its feasibility
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

28. Nikos-MOMENT Target Studies
conclusions
In the case of Hg-jet:
physical parameters as tilt angle, radius, length optimized
further shielding optimization
feedback from EMuS studies on neutron radiation
Important to proceed with R&D for the granular waterfall:
only 20% less yields than Hg-liquid jet using DEM analysis parameters
simulations for further physical parameters optimizations and experiment for validation, IHEP and C-ADS target group/IMP
target solution of multi-MW neutrino and muon beams
Thanks
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

29. inversed 1st degree polynomial field:
field approximation implemented in FLUKA:
L = 5, 10, 15, 20, 50 m
The question is what do we prefer muons or pions
5 m

30. Waterfall granular target for MOMENT - I
granular waterfall
L = 5 m, 5 - SC coils
rm = 20 cm to 40 cm
14 T to 3 T
Hg-jet might not be applicable for high power targetry in neutrino beams
High toxicity (Hg-pool) , severe radiation damage on the shields due to high Z (Chin.Phys. C40 (2016) no.12, ), also jet kinematic limits due to interaction with 14 T
Topic studied and presented at NuFact15-16 workshops, also studied in International Neutrino Factory
Tungsten waterfall granular target
Fluidized <-> heat removal/exchange -> recyclable, less radiation (smaller Z)
Preliminary studies on the waterfall parameters and radiation with FLUKA and Discrete Element Methods MCs (NuFact16 workshop, “Phys.Rev.Accel.Beams 20 (2017) no.2, ”), on-going
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

31. simulation representation (in FLUKA)
figure of merit:
π, μ, p yields, distributions downstream of:
the Main Capture Solenoid (MSC)
Adiabatic Transport Solenoid
Main Capture Solenoid
“idealized” field
B = 14 T, LMCS= 32 cm, rMCS= 20 cm
study tilts, lengths, radii, beam-sizes
Gaussian field approximation at MCS
MSC
Bz= 14 T -> 3 T
----->--->-->->
Adiabatic Transport Solenoid
L = 5, 10, 15, 20, 35, 50 m
r = 20 cm - > 43.2 cm
B = 14 T -> 3 T
Bz= 14 T
--->--->--->
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

32. MOMENT - Target Station: G4 vs FLUKA
Zhao Guang, IHEP/ CAS
similar shape, slightly different scale
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

33. Nikos-MOMENT Target Studies
Granular waterfall in the strong magnetic field
The grains would be charged by proton, the deflecting force, however, would be small enough.
mass flow rate: kg/s
charging rate: 10 mA/s
electric quality: ~1.6E-4 C/kg
velocity: ~ 3 m/s
magnetic: 15 T
deflecting force: ~ 7.2E-3 N/kg
Usually, the equivalent grounding resistance is finite, Thus, this force should be much smaller.
Low electric conductivity and magnetic susceptibility to avoid shape transformations and instabilities of the waterfall.
Tungsten carbide:
Magnetic susceptibility (~ +5.0E-9, ~ 1.7E-4 times that for Hg).
Electric conductivity (< 400 S/m, ~ 4.0E-4 times that for Hg).
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

34. Power deposit (8 GeV & 0.5mA)
Cai Hanjie/ IMP, CAS
A much smaller power deposited in unit mass of waterfall target

35. Nikos-MOMENT Target Studies
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

36. Beam escaping
The percent of the escaped beam (after main target) is quite large.
The granular flow in the chute can act as second target and produce additional pions.

37. Nikos-MOMENT Target Studies
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

38. Nikos-MOMENT Target Studies
NuFact17-Sep 2017
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39. Nikos-MOMENT Target Studies
NuFact17-Sep 2017
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40. Nikos-MOMENT Target Studies
NuFact17-Sep 2017
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41. Nikos-MOMENT Target Studies
Recalculation of the neutrino fluxes with FLUKA, μ+ and μ- beams assuming 100% charge separation and channel transmission
detector @ 150 km - νμ νμ μ+ νe μ- - νe
detector @ 150 km μ+ μ-
Ν ν (x1012)
/ m2 / 1024 p.o.t.
<E> MeV
Ν ν (x1011) νμ -
5.76
183
1.46
200 νe
1.42
193
5.84
175 -
stat. error ~ 1.5% -
NuFact17-Sep 2017
Nikos-MOMENT Target Studies

42. Why is this research important ?
MOMENT -> Option after JUNO -> Neutrino Factory -> Ultimate future machine for accelerator produced neutrinos, a dream machine of many
MOMENT Target Station <-> Muon Collider Target station -> Future option in collider physics
NV- IHEP Report 2017