Letter of Intent to host Miniball at RIBF
N. Aoi1, H. Baba2, A. Blazhev3, F. Browne2, C. Campbell4,
M. Carpenter5, A. Corsi6, M.L. Cortés2, H. Crawford4, M. Cromaz4,P. Doornenbal2, P. Fallon4, A. Gillibert6, H. Hess3, E. Ideguchi1,
T. Isobe2 , J. Jolie3, V. Lapoux6, H. Liu8, A. Macchiavelli4, O. Möller8,
M. Niikura7, S. Nishimura2, A. Obertelli8, V. Panin6, N. Pietralla8,
P. Reiter3, L. Riley9, H. Sakurai2,7, M. Seidlitz3, D. Suzuki2, S. Thiel3,
V. Werner8, N. Warr3, K. Wimmer7,2 and Y. Yamamoto1
1

Research Center for Nuclear Physics, Osaka University, Osaka, Japan
2
RIKEN Nishina Center, Wako, Japan
3
Institut für Kernphysik, Universität zu Köln, Cologne, Germany
4
Nuclear Science Division, Lawrence Berkeley National Laboratory,
Berkeley, USA
5
Physics Division, Argonne National Laboratory, Argonne, USA
6
CEA, Centre de Saclay, Gif-sur-Yvette, France
7
Department of Physics, University of Tokyo, Tokyo, Japan
8
Institut für Kernphysik, Technische Universität Darmstadt,
Darmstadt, Germany
9
Department of Physics and Astronomy, Ursinus College, Collegeville,
USA
November 27, 2018

1 Introduction
Since its first beam in 2006, the Radioactive Isotope Beam Factory (RIBF) of the RIKEN Nishina
Center (RNC) provides highest intensity primary beams at 345 MeV/u. The great potential of the
facility is best demonstrated by the search and discovery of more than 100 new isotopes [1, 2, 3,
4, 5, 6] using intense primary beams at the fragment separator BigRIPS [7]. In addition to 238 U,
primary beams at the RIBF include 18 O, 48 Ca, 70 Zn, 124 Xe, and 78 Kr. In-beam γ-ray spectroscopy
experiments using secondary beams typically employ the ZeroDegree spectrometer [7] for reaction
product identification and the DALI2 NaI(Tl) scintillator array [8] for γ-ray detection. Owing to thehigh secondary beam intensities as well as detection efficiency, experiments performed at the RIBF
with the most exotic nuclei are feasible nowhere else in the world. Notable examples of the RIBF’s

12

2 Physics casecapabilities include the first γ-ray spectroscopy of 54 Ca [9], 78 Ni [10], and 70 Kr [11]. Overall, inbeam γ-ray experiments currently account for about 40 % of the physics publications from NP-PAC
approved experiments at the RIBF with fast radioactive beams. A complete list of obtained results
to date can be found on the SUNFLOWER web-page [12].
So far, spectroscopic experiments have been largely limited to even-even nuclei in the vicinity ofshell closures. Using a germanium based γ-detector will significantly enhance the capabilities of the
RIBF facility and open new possibilities for experiments. Spectroscopic studies of nuclei with higher
level density and lifetime measurements by Doppler-shift techniques will become possible. This Letterof Intent proposes to combine the Miniball array [13] with the BigRIPS fragment separator and the
ZeroDegree spectrometer. This combination of the worlds highest secondary beam intensities with a
Ge based γ-ray spectrometer will provide unique opportunities for nuclear structure as well as nuclear
astrophysics studies.

2 Physics case
The RIBF provides currently worldwide uniquely high secondary beam intensities at intermediate
energies ranging from 100 to 300 MeV/u. The proposed addition of the high resolution Ge-based γray spectrometer Miniball will allow to access the most exotic nuclei and thus unprecedented science.
Unique to the RIBF is the availability of a high intensity 238 U beam, giving access to the mostneutron-rich nuclei around 78 Ni as well as heavier nuclei beyond 132 Sn, which are of importance forthe astrophysical r-process [14]. γ-ray spectroscopy experiments in this region of the nuclear chart
can to date only be performed at the RIBF.
Shell evolution towards the drip-lines, new magic numbers
Neutron-rich nuclei below 78 Ni display many interesting features: Halo systems have now beensuggested at N ∼ 20 [15], while the classic shell gaps N = 20, 28 disappear for neutron-richnuclei resulting in a large region of deformation [16, 17]. Lifetime measurements for excitedstates in suggested halo nuclei would provide an independent measure of the L = 1 character
through large M 1 and E2 transitions. Tracking the evolution of the neutron f7/2 and p3/2 fromN = 20 to 28 requires detailed spectroscopy of the even-odd nuclei. So far, this has only beenaccomplished for the Si isotopes [18] up to N = 26. Neutron knockout reactions with Ne or Mg
isotopes would particularly benefit from the improved resolving power of Miniball compared to
DALI2.
In the calcium isotopic chain two new sub-shell closures have been established experimentallyat N = 32, 34 [9, 19, 20]. Theoretical calculations [21] show that three-nucleon forces play animportant role in the microscopic description of these nuclei. Spectroscopy of Ca isotopes at
RIBF has recently been extended to N = 36 for 2+
1 states and single-particle properties studied
in the neutron and proton removal reactions from 54 Ca within the SEASTAR project [22].
Beyond Ca, the Ti isotopes show a staggering of collectivity which is not yet understood ineither beyond mean field [23] as well as shell model [24] calculations. Lifetime measurements
beyond the 2+ states, states in the odd-N Ca and Ti isotopes, as well as spectroscopic factors
obtained from knockout reactions will provide more stringent tests of the robustness of theclosed-shell cores and the role of three-body forces for non-magic isotopes. Generally, due to theonset of collectivity and complexity of the level structures, odd-even nuclei beyond Z = 20 havebeen challenging with DALI2, as seen already for 55 Sc [25]. An abundance of new spectroscopic
details may be revealed by utilizing Miniball.
Collectivity and breakdown of the harmonic oscillator shell closure at N = 40 has been established through measurements of collective properties, excitation energies, and level lifetimes (seefor example Refs. [26, 27, 28] for most recent experimental data). A new island of inversion has
been predicted with a center at 64 Cr [29]. Experimental data on spin and parity assignments aswell as level occupations is sparse in the region of neutron-rich N = 40 nuclei. High-resolution
spectroscopy of the even-odd nuclei 67,69 Fe, 63,65 Cr, and 57,59 Ti from one-neutron knockout
reactions will fill this gap and reveal whether its inversion extends down towards 60 Ca.

2

2 Physics case3

Excited states in 78 Ni and 79 Cu have recently been studied at the RIBF facility with a highintensity 238 U primary beam [10, 30]. Tracking the evolution of the shell gaps along N = 50 and
Z = 28 as predicted in Ref. [31] requires precise measurements of odd nuclei through knockout
reactions. Lifetime measurements of neutron-rich Zn, Ge, and Se nuclei with N > 50 to delineate
the onset of collectivity beyond 78 Ni will be possible as well.
Lifetime measurements and spectroscopy of odd-A nuclei in the region of doubly-magic 132 Sn
will provide constraints for shell model calculations in the region south-east of 132 Sn where
spectroscopy so far is sparse. This region is extremely important to understand nucleo-synthesisin the r-process and shell evolution in heavy nuclei. The filling of the 2f7/2 orbital in Sn isotopes
beyond 132 Sn resembles the situation in the Ca isotopes, and a new magic number is predicted
at N = 90 [32], but precise single particle spectroscopy and their evolution along the Sn isotopic
chain beyond N = 83 are not yet available from experiment.
N = Z: the rp-process, mirror symmetry, and the quest for 100 Sn
Along the N = Z line of the nuclear chart, a number of interesting physics cases can be studied.
Proton-rich nuclei along N = Z constitute the path of the rapid proton-capture process (rpprocess), that powers type I X-ray bursts. While direct measurements of (p, γ) reaction rates onthese radioactive isotopes are not feasible in all cases, indirect measurements of excited statesin the final nuclei as well as spectroscopic factors from (d,n) reactions can significantly reduce
the uncertainties associated with the calculation of element abundances in the rp-process [33].
N ∼ Z nuclei also provide an interesting testing ground to investigate the breaking of charge
symmetry and charge independence. Measurements of Coulomb energy and mirror energy differences have been limited so far to A = 70 and low spin values [34, 11]. Data for higher (medium)spin values and odd-even nuclei are required to clarify the role of isospin-non-conserving forces
and neutron skin effects [35]. The high intensity 78 Kr and 124 Xe primary beams at RIBF combined with the high in-beam energy resolution of Miniball allow for detailed spectroscopy of
nuclei between A = 50 and 100. In addition to nuclear structure information, new data on
waiting point nuclei of the rp-process predicted in this region can be obtained.
The region around 100 Sn has attracted a lot of interest. B(E2) values in light tin isotopes arelarger than expected [36, 37], and the ordering of the neutron νg7/2 and νd5/2 orbitals above
N = 50 seems to be inverted [38]. Spectroscopy of 101,103 Sn and 101,103 In through proton or
neutron knockout and well as (p, p′ ) with the MINOS liquid hydrogen target [39] will contributeto the understanding of unexpected high collectivity in the light even-even Sn nuclei.
Shape evolution and coexistence around A ∼ 100 and in the rare earth region
Between N = 50 and N = 82, nuclei show an interesting interplay of single-particle and collective excitation modes. In the Sr and Zr isotopes, a sudden onset of collectivity at N = 60,
which extends at least to 110 Zr [40], is accompanied with shape coexistence at low excitationenergies [41, 42]. Detailed spectroscopy of odd-mass in this region will help unravel the orbitals
involved. In contrast, for the Kr isotopes a drop in the 2+ excitation energy associated withan onset of deformation is not observed [43, 44]. Additional information could come from lifetime measurements and off-yrast spectroscopy through secondary fragmentation reactions andspectroscopy of odd-even nuclei.
High intensity radioactive beams with Z & 50 are unique to the RIBF facility. Measurements ofcollective properties, excited state lifetimes, and proton inelastic scattering will shed new lighton the evolution of collectivity and shape coexistence in the rare earth region. Measurementsof single-particle properties will give hints on the underlying microscopic structure and new
constraints for astrophysical r-process calculations.
Octupole collectivity in A ∼ 90 and 140 nuclei
In regions where neutrons and protons occupy orbitals at the Fermi surface with ∆j = ∆ℓ = 3,strong octupole correlations can break the reflection symmetry of nuclei resulting in octupole
deformed shapes. Octupole collectivity is expected in the Ra-Th region, and for neutron-rich

34

3 In-beam γ-ray spectroscopy at the RIBF

Figure 1: Overview of the RIBF facility. Not shown are the initial acceleration states. The BigRIPS
fragment separator is used to purify and identify the radioactive ion beams. In-beam γ-ray
spectroscopy is performed at the focal point F8. Reaction products are uniquely identified
using the ZeroDegree spectrometer (F8 - F11).

nuclei in the region around 144 Ba [45] and 90 Se. In the first case, it would be interesting to see
if the region of octupole deformation extends to other nuclei, i.e. Xe or Ce, or the proton-odd
neighbors. (p, 2p) reactions on the MINOS liquid hydrogen target [39] enable the population of
excited states in this region. The combination with high-resolution γ-ray spectroscopy opens,for the first time, also access to odd isotopes. Moreover, such reactions will shed new light on
the single-particle structures underlying the collective states. Around A = 90, first spectroscopyof 90 Se has only been performed recently [46], and information beyond the mere location ofstates is necessary to asses the onset of octupole deformation, for example by means of lifetime
measurements.

3 In-beam γ-ray spectroscopy at the RIBF
It is proposed to couple the Miniball array with BigRIPS fragment separator and the ZeroDegree spectrometer at the RIBF. Experimental details are briefly described in the following section, highlighting
the unrivaled possibilities for in-beam γ-ray spectroscopy experiments offered at the RIBF.

3.1 The RIBF facility
The facility for radioactive isotope research is schematically shown in Figure 1. Stable beams areaccelerated up to 345 MeV/u using a linear accelerator followed by four cyclotrons. Primary beam
intensities for this energy are summarized in Table 3.1.

4

3.2 BigRIPS and ZeroDegree Spectrometerbeam particle
18

O
Ca1
70
Zn
78
Kr
124
Xe
238
U
48

5
beam current [pnA]
maximum expected
1000
730
250
480
100
58

500
500
200
300
80
402

1 48
2

Ca might not be available in 2020.
In fall 2018, a stable primary beam
intensity of 60 pnA was maintainedfor 238 U.

Table 1: Primary beam intensities at 345 MeV/u [47] for the facility operation in FY2018. Maximum
achieved and expected beam currents are given in pnA.

3.2 BigRIPS and ZeroDegree SpectrometerPrimary beams impinge on the production target (F0); their fragmentation or fission products aresubsequently separated in the two-stage separator BigRIPS. Event-by-event identification is facilitatedby Bρ, ∆E, and time-of-flight measurements between the focal points F3 and F7. Positions and angles
of beam particles are measured using parallel plate avalanche counters (PPAC), the time-of-flight ismeasured with plastic scintillators at F3 and F7. At F7, an ionization chamber allows for unique
Z identification through an energy loss measurement. Maximum rates are several tens of kHz. The
total momentum acceptance amounts to ±3 %, with a momentum resolution of 3440. A relative
A/Q resolution of 0.034 % has been achieved [48], allowing for the separation of fully stripped fromhydrogen-like charge states. Production cross sections of radioactive ions have been measured for awide range of nuclei [2, 5, 6] providing validation of the theoretical fragmentation and fission crosssections employed in LISE++ simulations. Secondary beam intensities for experiments can therefore
be predicted reliably, allowing for an straightforward planning of experiments at the RIBF.
In-beam γ-ray spectroscopy experiments are typically performed with thick solid secondary reaction
targets (Be, C, Au, Pb, etc.) at F8 in the order of 1 g/cm2 depending on the case of interest. The sizeof the beam spot on the target amounts typically to σ = 5 mm in X and Y. Tracking of the beam onto
the target is facilitated by a set of two PPACs in front of the target (position resolution σ = 0.7 mm),the scattering angle can be reconstructed using a third PPAC behind the target (in front of STQ17 in
Figure 1) with an accuracy of ≈5 mrad [37]. For the campaign of Miniball at the RIBF, we envision
to use solid targets, the liquid hydrogen target MINOS [39], or a plunger for lifetime measurements.
For experiments with solid targets, the present setup at F8 with three PPACs and a beam pipe of
150 mm diameter is used, allowing to place the γ-ray detectors close to the target to maximize theefficiency.
The ZeroDegree spectrometer is used for identification of reaction products behind the secondary
target located at F8 (see Figure 1). Particle identification is obtained in an analogous way to the
BigRIPS separator by using Bρ, ∆E, and time-of-flight measurements between F8 and F11. Typicalbeam energies after the target amount to 100 − 200 MeV/u. Therefore, for high Z nuclei not all
reaction products will be in the fully stripped charge state. With the high resolution for the mass
to charge ratio A/Q it is possible to discriminate different charge states up to Z ≈ 55, A ≈ 150.
Additionally, a total kinetic energy detector can be placed at the end of the beam-line after the last
ionization chamber at F11. Three different optics modes are possible for the ZeroDegree spectrometer:
Large acceptance, high resolution, and dispersive. With a momentum resolution of p/∆p = 1240, thelarge acceptance mode offers sufficient accuracy for parallel momentum distributions to deduce angularmomentum L assignments.

5

6

3 In-beam γ-ray spectroscopy at the RIBF

3.3 Miniball at RIBF

10

DALI2 (a)8

∆ Eγ /Eγ (%)∆ Eγ /Eγ (%)

In-beam γ-ray spectroscopy at the RIBF has so far been mostly restricted to the spectroscopy of eveneven nuclei. Spectroscopy of odd nuclei is challenging due to the limited energy resolution, except for
certain cases close to magic numbers [25, 30]. The in-beam energy resolution depends critically on
the intrinsic energy as well as position resolution, as shown in Figure 2 (a).

10

8

6

6

4

4

2

2

0
0

20 40 60 80 100 120 140 160 180

laboratory detection angle θ (deg)00Miniball (b)intrinsic resolution
velocity uncertainty
angle uncertainty
total

20 40 60 80 100 120 140 160 180

laboratory detection angle θ (deg)Figure 2: Energy resolution of Miniball (b) in comparison with DALI2 (a). The total in-beam energy
resolution (black) depends on the intrinsic energy resolution (blue), the position resolution
for the Doppler correction (green), as well as the velocity uncertainty due to the energy loss
in the target (red). Uncertainties are calculated for a 200 MeV/u beam impinging on a 4 mm
Be secondary target (hβi = 0.55, ∆β = 0.016) emitting a 1 MeV γ ray. Great improvementsin the intrinsic energy as well a position resolution of Miniball compared to DALI2 allow forspectroscopy with about 2–3 % final energy resolution for in-beam experiments. Doppler
correction on the segment level was assumed for this plot.
With Miniball, the obtainable energy resolution following Doppler correction depends on exact
distance to the target, the energy and mass of the secondary beam, and the secondary target thickness.
Figure 2 shows the parameters of a typical in-beam γ-ray experiment at the RIBF. Assuming a distanceof 200 mm from the target, the resolution with Miniball is improved by a factor three compared to
DALI2. For larger distances between detectors and target, better resolutions can be obtained.
The nominal efficiency of Miniball amounts to 7.8 % at 1.3 MeV [13] using add-back. For experiments at RIBF, the distance to the target is larger than for the typical experiments performed at
REX-ISOLDE. Thus, a reduced efficiency is expected. For experiments with fast beams performed at
GSI, the array was placed at angles of 51 and 85◦ at about 220 mm distance, resulting in an efficiencyof 3 % at 1.3 MeV [49]. For experiments at the RIBF, we plan to install six clusters at 30◦ andtwo clusters at 65◦ at a distance of 200 mm from the target. The in-beam full energy peak (FEP)
efficiency at 1 MeV in this case is 4.1 % and 1.1 %, respectively for the detectors at 30 and 65◦ .
Typical resolutions are on the order of 2–3 % (FWHM) after Doppler correction, depending on thetarget thickness and the beam properties.
Experiments at RIBF typically involve low beam intensities. The maximum total rate at F8 is a
few tens of kHz. Reactions at relativistic energies on the secondary targets produce some particle
background, but the flux is low, such that there is no radiation damage of the detectors from, forexample, neutrons.

63.4 Ancillary detectors

7

3.4 Ancillary detectors
It is planned to couple Miniball to other Ge detector systems. Discussions are ongoing to use thetracking detectors from Lawrence Berkeley National Laboratory (triplet GRETINA prototype), RCNP
Osaka (quad GRETINA-type), and TU Darmstadt (DAGATA triple) to maximize the efficiency andresolution. The planned configuration of the array is shown in Figure 3.

Figure 3: Setup in the simulation. The beam is coming from the lower right impinging on the target
located at the center of the array. Six Miniball clusters are located at 30◦ , two at 65◦ ,additional tracking γ-ray detectors are also located at 65◦ .
GEANT4 [50] simulations for the Miniball array in addition to the ancillary detectors were initially
carried out for a 1 MeV γ ray emitted at 100 MeV/u. The in-beam resolutions amounted to 0.15 −1.56 % (σ) for the ideal no target case and 0.33 − 2.54 % (σ) for a realistic reaction on a 3 mm thickBe secondary target. The total in-beam FEP efficiency amounted to 9.4 %.

4 Simulation results, expected performance
In order to estimate the performance of the proposed array combining the Miniball cluster detectors with γ-ray tracking detectors GEANT4 simulations have been carried out under experimental
conditions. These included a realistic geometry of the detectors, the crystals and the cryostats, aswell as the beam pipe. The reaction dynamics of knockout and inelastic scattering reactions were
implemented through a parametrization of the ejectile momentum and angular distributions. In theanalysis of the simulated data, the Doppler correction was performed assuming the Miniball segmentwith the highest energy deposition recorded the first interaction of the γ-ray. For the angle, theweighted average position of hits in the segment was used in addition to the scattering angle of theejectile. An event-by-event mid-target velocity β was reconstructed from the ejectiles momentum
distribution. Add-back analysis was performed based on the link algorithm within a clustering angleof 20◦ . Tracking was implemented for the ancillary detectors described above.
First spectroscopy of excited states of the N = 50 nucleus 79 Cu has been recently performed at
RIBF using DALI2 [30]. With a limited intrinsic and in-beam resolution, the construction of the level
scheme is largely guided by comparison to theoretical calculations. Figure 4 shows a simulation of theexperiment using either DALI2 or the Ge based array using eight Miniball and three tracking clusters.
The number of emitted γ rays is identical in both simulations. The improved resolution with the Ge
based detectors permits unambiguous identification of faint lines in the spectrum.

7

104

existing arrayhigh resolution array

103

103
102

counts / 4 keV

4 Simulation results, expected performancecounts / 20 keV

8

102
10

500

1000 1500 2000 2500 3000 3500 4000 4500

Eγ (keV)

2500

250
existing array

2000

high resolution array

200

1500

150

1000

100

500

50

0
1000

1500

2000

2500

3000

3500

4000

4500

counts / 5 keV

counts / 50 keV

Figure 4: Simulation of the one-proton knockout reaction from 80 Zn to 79 Cu in comparison withDALI2. The simulated DALI2 data correspond to the results from a recent RIBF experiment [30].

0Eγ (keV)Figure 5: Simulation of the one-proton knockout reaction from 56 Ti to 55 Sc using Miniball (green) incomparison with DALI2 (black). The simulated DALI2 data correspond to the results froma recent RIBF experiment [25].

As the new N = 34 sub-shell closure between the neutron 2p1/2 and 1f5/2 orbitals is only observed in
the Ca isotopes, and not in the heavier Ti isotopes, the intermediate isotope 55 Sc located in-between
is of key interest. Spectroscopy of this nucleus can clarify this peculiar behavior which, so far, is
not fully understood. Spectroscopy of 55 Sc has been performed [9] with DALI2. The comparison isshown in Figure 5. A realistic background obtained from the experiment has been implemented in
the simulation. The improved resolution using high-resolution γ-ray detectors is evident, allowing
for simultaneous lifetime measurements which were so far experimentally inaccessible. Furhtermore,
the superb peak-to-background ratio allows for gating on individual transitions to measure final state8

counts / keV

5 Requested equipment, support, and maintenance

9

10 4

10

3

10

2

10

no lifetime effects
lifetime effects

1

100

200

300

400

500

600

700

800

900

Eγ (keV)146
Figure 6: Simulation of lifetime effects. The decay of the 3−
Ba to the ground state and1 state in++through the 2 and 4 states has been simulated with realistic lifetimes (green) and without
any lifetime effects (black).

exclusive momentum distributions and thus assign spin and parity quantum numbers to the levels
populated in the knockout reaction. The narrow peak width also reduces the background in the γ − γcoincidence matrix used to construct the level scheme.
In fact, the prospect to perform lifetime measurements emerges as further immense benefit of highresolution spectroscopy in combination with fast radioactive beams. This possibility is explored in
Figure 6. Here, the simulation compares Coulomb excitation of 146 Ba with and without the wellknown level lifetimes. The decay of the 3− state with a half-life of 237 ps feeds the 2+ and 4+ statesin addition to the ground state (821 keV transition). The 2+ state has a long half-life of 0.859 ns,
which results in a very long tail. Unknown lifetimes can be measured by comparing the measured
γ-ray energy spectrum to simulations with varying lifetimes and fitting the best matching lifetime tothe data [51].

5 Requested equipment, support, and maintenanceWe intend to host eight Miniball triple clusters for the calendar year 2020. In addition, we requireparts of the filling system and the liquid nitrogen hoses. The support structure for Miniball may beobtained from the University of Cologne.
The DGF based data-acquisition system used so far for Miniball is not needed. Instead, the dataacquisition will be provided by this collaboration. Specifically, digitizers based on the GRETA designfrom the CAGRA project [52] will be used for the Miniball detectors. This acquisition system will be
integrated in the RIBF DAQ framework and correlated with the BigRIPS and ZeroDegree systems
by time-stamping or common trigger. Further funds for the digitizers and trigger modules for the
ancillary detectors within the array have been requested from the Japanese Society for the Promotionof Science.
The RIBF has ample experience with hosting Ge detector arrays, for example hosting EURICA
from 2012–2016 [53, 54]. Parts of the infrastructure from the EURICA campaign exists and can beused for Miniball. A reliable liquid nitrogen filling system is available and will be extended. High
voltage supply, monitoring, and temperature monitoring systems as well as an uninterruptible power

910

Referencessupply unit will be provided by the RIBF.
Packing and transportation costs of the detectors from CERN, or elsewhere, will be provided by
RIKEN. Travel and local support for members of the Miniball collaboration for dismounting at CERN
and setup at RIBF will also be provided. This includes on-site maintenance during the experiment incase needed.

6 Project Time-Line
In parallel to this Letter of Intent, the collaboration has submitted a construction proposal to thenext RIBF Nuclear Physics Program Advisory Committee. This construction proposal includes theancillary detectors as well. The decision on the proposal will be made at the NP-PAC meeting inNovember 2018.
A dedicated workshop will be held in spring 2019, either at RIBF or in Europe, to discuss thephysics proposals and details of the setup. The call for nuclear physics proposals to the NP-PAC isusually issued in July/August with a submission deadline in October 2019. This call will explicitly
solicit proposals for Miniball and the ancillary devices. Application for beam time is open to all
RIBF users. Beam-time will be awarded based on the recommendation by the NP-PAC committee
in their meeting in December 2019. The RIBF will allocate 30 days of beam on target time for theexperimental campaign in spring 2020 and further beam time in fall 2020 depending on the NP-PAC
recommendation. Within these campaigns, we anticipate about 10 experiments.

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