A series of beam dynamic studies were performed in 2020-2021 at the PIP-II Injector Test Facility (PIP2IT) that has been built to validate the concept of the front-end of the PIP-II linac being constructed at Fermilab. PIP2IT is comprised of a 30-keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1- MeV CW RFQ, followed by a 10-m Medium Energy Beam Transport (MEBT), 2 cryomodules accelerating the beam to 16 MeV and a High-Energy Beam Transport (HEBT) bringing the beam to a dump. This paper presents beam dynamics - related measurements performed at PIP2IT such as the Twiss parameters with Allison scanners, beam envelopes along the injector, and transverse and longitudinal rms emittance reconstruction. These measurements are compared with predictions from the beam dynamics code Tracewin.

The PIP-II Injector Test 1 PIP2IT facility accelerator was assembled in multiple stages in 2014 $-$ 2021 to test concepts and components of the future PIPII linac that is being constructed at Fermilab. In its final configuration, PIP2IT accelerated a 0.55 ms x 20 Hz x 2 mA H$-$ beam to 16 MeV. To protect elements of the beam line, a Machine Protection System MPS was implemented and commissioned. The beam was interrupted faster than 10$\mu$s when excessive beam loss was detected. The paper describes the MPS architecture, methods of the loss detection, procedure of the beam interruption, and operational experience at PIP2IT.

In modern high intensity ion-particle accelerators, a Radio Frequency Quadrupole (RFQ) is utilized to prepare a high-quality beam for injection to the main accelerating section. Since an RFQ governs the initial beam parameters, characterization of the beam coming out from the RFQ is foremost step toward commissioning of an accelerator facility. It allows validating the RFQ design as well as attaining a better understanding of charged-particle beams. This paper describes the beam-performance of the Proton Improvement Plan-II Injector Test (PIP2IT) Continuous Wave (CW) four vane-type RFQ. It is designed to operate at a frequency of 162.5 MHz and accelerate a nominal H- beam of 5 mA from 30 keV to 2.1 MeV. The paper details beam tests performed to validate the RFQ design specifications for transmission, beam kinetic energy and, RMS emittances. The paper also presents beam profile measurements and implication of the beam-jitters on the effective beam emittance at the RFQ exit.

Transverse 2D phase space distributions of a 2.1 MeV, 5 mA H- beam are measured at the Proton Improvement Plan II Injector Test accelerator at Fermilab with an Allison scanner. This paper describes the design, calibration, and performance of the scanner along with the main results from beam measurements. Analyses of the recorded phase portraits are performed primarily in action-phase coordinates. The stability of the action under linear optics makes it easier to compare measurements taken under different beamline conditions. The amplitude of a single measured point ("pixel") is proportional to the phase density in the corresponding portion of the beam. When the Twiss parameters are calculated using only the high-phase density part of the beam, the pixel amplitude in the beam core is found to be decreasing approximately exponentially with action and to be phase-independent. Outside of the core, the amplitudes decrease with action at a slower rate than in the core. This "tail" comprises 10%-30% of the beam, with 0.1% of the total measured intensity extending beyond action 10-20 times larger than the rms emittance. The transition from the core to the tail is accompanied by the appearance of two "branches" that are separated in phase and extend beyond the core. A set of selected measurements shows that there is no measurable emittance dilution along the beamline; the beam parameters are practically constant over a 0.5 ms pulse; and scraping in various parts of the beamline is an effective way to decrease the transverse tails by removing the branches.

The warm front end of the PIP2IT accelerator, assem-bled and commissioned at Fermilab, consists of a 15 mA DC, 30 keV H- ion source, a 2 m long Low Energy Beam Transport (LEBT) line, and a 2.1 MeV, 162.5 MHz CW RFQ, followed by a 10 m long Medium Energy Beam Transport (MEBT) line. A part of the commissioning efforts involves operation with the average beam power emulating the operation of the proposed PIP-II accelera-tor, which will have a duty factor of 1.1% or above. The maximum achieved power is 5 kW (2.1 MeV x 5 mA x 25 ms x 20 Hz). This paper describes the difficulties encoun-tered and some of the solutions that were implemented.

The central part of PIP-II program of upgrades pro-posed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in super-conducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype was installed in the PIP-II Injector Test (PIP2IT) accelerator and successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.

Fermilab is undertaking the development of a new 800 MeV superconducting RF linac to replace its present normal conducting 400 MeV linac. The PIP-II linac warm front-end consists of an ion source, LEBT, RFQ and MEBT which includes an arbitrary pattern bunch chopper, to generate a 2.1 MeV, 2mA Hbeam. This is followed immediately by a series of superconducting RF cryomodules to produce a 800 MeV beam. Commissioning, operate and safety present challenges to the beam instrumentation. This paper describes some of the beam instrumentation choices and challenges for PIP-II. THE PIP-II ACCELERATOR The PIP-II project at Fermilab is building a superconducting Linac to fuel the next generation of intensity frontier experiments [1]. Capitalizing on advances in superconducting radio-frequency (SRF) technology, five families of superconducting cavities will accelerate H− ions to 800 MeV for injection into the Booster. Upgrades to the existing Booster, Main Injector, and Recycler rings will enable them to operate at a 20 Hz repetition rate and will provide a 1.2 MW proton beam for the Long Baseline Neutrino Facility. Table 1 list keep beam parameters for PIP-II. Table 1. PIP-II Beam Parameters Linac PIP-II Delivered Beam Energy (kinetic) 800 MeV Particles per Pulse 6.7 × 10 12 Average Beam Current in the Pulse 2 mA

The Proton Improvement Plan, Stage Two (PIP-II), is a program of upgrades proposed for the Fermilab injection complex, the central part of which is an 800 MeV, 2 mA CW-compatible SRF linac. A prototype of the PIP-II linac front-end called the PIP-II Injector Test (PIP2IT) is being built at Fermilab. As of now, a 15 mA DC, 30 keV H[Formula: see text] ion source, a 2 m long Low Energy Beam Transport (LEBT), a 2.1 MeV CW Radio-Frequency Quadrupole (RFQ), followed by a 10 m Medium Energy Beam Transport (MEBT) have been installed and tested. A Fast Faraday Cup (FFC) installed in the MEBT measures the length of a beamlet cut out of the bunch by a small-size entrance hole of the FFC. The information about the bunch length measured at various settings allows for the reconstruction of the longitudinal beam dynamics and optimization of injection into the first cryomodule.

The Proton Improvement Plan, Stage Two (PIP-II) is a program of upgrades proposed for the Fermilab injection complex, which central part is an 800 MeV, 2 mA CW SRF linac. A prototype of the PIP-II linac front end called PIP-II Injector Test (PIP2IT) is being built at Fermilab. As of now, a 15 mA DC, 30-keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1 MeV CW RFQ, followed by a 10 m Medium Energy Beam Transport (MEBT) have been assembled and commissioned. The MEBT bunch-by-bunch chopping system and the requirement of a low uncontrolled beam loss put stringent limitations on the beam envelope and its variation. Measurements of transverse and longitudinal beam dynamics in the MEBT were performed in the range of 1-10 mA of the RFQ beam current. Almost all measurements are made with 10 μs beam pulses in order to avoid damage to the beam line. This report presents measurements of the transverse optics with differential trajectories, reconstruction of the beam envelope with scrapers and an Allison emittance scanner, as well as bunch length measurements with a Fast Faraday Cup.

The Warm Front End (WFE) of the Proton Improvement Plan II Injector Test at Fermilab has been constructed to its full length. It includes a 15-mA DC, 30-keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT) with a switching dipole magnet, a 2.1 MeV CW RFQ, followed by a Medium Energy Beam Transport (MEBT) with various diagnostics and a dump. This report presents the commissioning status, focusing on beam measurements in the MEBT. In particular, a beam with the parameters required for injection into the Booster (5 mA, 0.55 ms macro-pulse at 20 Hz) was transported through the WFE.

In a low energy beam transport line (LEBT), the emittance growth due to the beam's space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern usually changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report introduces the rationale for the proposed scheme and formulates the physical arguments for it as well as its limitations. An experimental realization of the scheme was carried out at Fermilab's PIP2IT where low beam emittance dilution was demonstrated for a 5 mA, 30 keV H- beam.

Typical front-ends of modern light-ion high-intensity accelerators typically consist of an ion source, a Low Energy Beam Transport (LEBT), a Radiofrequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT), which is followed by the main linac accelerating structures. Over the years, many LEBTs have been designed, constructed and operated very successfully. In this paper, we present the guiding principles and compromises that lead to the design choices of the PXIE LEBT, including the rationale for a beam line that allows un-neutralized transport over a significant portion of the LEBT whether the beam is pulsed or DC.

improvements to achieve multi-MW capabilities at Fermilab. PIP-II is based on three major thrusts. They are (1) the recently completed upgrades to the Recycler and Main Injector (MI) for the NOvA experiment, (2) the Proton Improvement Plan [3] currently underway, and (3) the Project X Reference Design [4]. Note that: The Proton Improvement Plan (PIP) consolidates a set of improvements to the existing Linac, Booster, and Main Injector (MI) aimed at supporting 15 Hz Booster beam operation. In combination, the NOvA upgrades and PIP create a capability of delivering 700 kW beam power from the Main Injector at 120 GeV; The scope of the Project X Reference Design Report was aimed well beyond PIP. It described a complete concept for a multi-MW proton facility that could support a broad particle physics program based on neutrino, kaon, muon, and nucleon experiments [5,6]. The Project X conceptual design has evolved over a number of years, incorporating continuous input on physics research goals and advances in the underlying technology development programs [7,8,9]. PIP-II, to high degree, inherits these goals as the goals for future developments and upgrades. This document (PIP-II Reference Design Report) describes an initial step in the development of the Fermilab accelerating complex. The plan described in this Report balances the far-term goals of the Laboratory's long baseline neutrino mission with the near- and mid-term goals identified at the Snowmass workshop [10] and endorsed by the P5 report [1].

A 2.1 MeV, 10 mA CW RFQ has been installed and commissioned at Fermilab's test accelerator known as PIP-II Injector Test. This report describes the measurements of the beam properties after acceleration in the RFQ, including the energy and emittance.

The PIP2IT test accelerator is under construction at Fermilab. Its ion source and Low Energy Beam Transport (LEBT) in its initial (straight) configuration have been commissioned to full specification parameters. This paper introduces the LEBT design and summarizes the outcome of the commissioning activities.

This paper presents the main results obtained during a series of beam measurements performed on the PIP-II Injector Test LEBT from November 2014 to June 2015. The measurements which focus on beam transmission, beam size and emittance at various locations along the beamline are compared with the beam dynamics code TRACK. These studies were aimed at preparing the beam for optimal operation of the RFQ, while evaluating simulation tools with respect to experimental data.

A CW-compatible, pulsed H- superconducting linac "PIP-II" is being planned to upgrade Fermilab's injection complex. To validate the front-end concept, a test accelerator (The PIP-II Injector Test, formerly known as "PXIE") is under construction. The warm part of this accelerator comprises a 10 mA DC, 30 keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1 MeV Radio Frequency Quadrupole (RFQ) capable of operation in Continuous Wave (CW) mode, and a 10 m-long Medium Energy Beam Transport (MEBT). The paper will report on the installation of the RFQ and the first sections of the MEBT and related mechanical design considerations.

The Proton Improvement Plan II (PIP-II) at Fermilab is a program of upgrades to the injection complex. At its core is the design and construction of a CW compatible, pulsed H- SRF linac. To validate the concept of the front-end of such machine, a test accelerator known as PIP-II Injector Test (PIP2IT) is under construction. It includes a 10 mA DC, 30 keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1 MeV CWRFQ, followed by a Medium Energy Beam Transport (MEBT) that feeds the first of 2 cryomodules increasing the beam energy to about 25 MeV, and a High Energy Beam Transport section (HEBT) that takes the beam to a dump. The ion source, LEBT, RFQ, and initial version of the MEBT have been built, installed, and commissioned. This report presents the overall status of the warm front end.

An Allison-type emittance scanner has been designed for PXIE at FNAL with the goal of providing fast and accurate phase space reconstruction. The device has been modified from previous LBNL/SNS designs to operate in both pulsed and DC modes with the addition of water-cooled front slits. Extensive calibration techniques and error analysis allowed confinement of uncertainty to the <5% level (with known caveats). With a 16-bit, 1MHz electronics scheme the device is able to analyse a pulse with a resolution of 1μs, allowing for analysis of neutralisation effects. This paper describes a detailed breakdown of the R&D, as well as post-run analysis techniques.