diff --git a/README.md b/README.md
index ebf53bb..2a61f9c 100644
--- a/README.md
+++ b/README.md
@@ -176,6 +176,15 @@ similar for `y_probes` and `z_probes`.
 The field probes provide human readable data for the electric and magnetic field components as a function
 of time, as well as some basic grid information to allow for convenient analysis.
 
+Additionally the time history of particle momentum and Poynting vector summed over the computational domain
+maybe output to a file `Data/momentum.dat` by setting
+
+```
+write_momentum = T,
+```
+
+in the `CONTROL` block of the `input.deck` file.
+
 ## Further Details
 
  - Information regarding the low noise PIC algorithm can be found in ExCALIBUR-NEPTUNE report 2047355-TN-03
diff --git a/example_decks/two_stream_neutral.deck b/example_decks/two_stream_neutral.deck
new file mode 100644
index 0000000..5f23e7c
--- /dev/null
+++ b/example_decks/two_stream_neutral.deck
@@ -0,0 +1,3 @@
+&control
+   problem = 'two_stream_neutral' 
+/
diff --git a/minepoch_py/momentum.py b/minepoch_py/momentum.py
new file mode 100644
index 0000000..162308e
--- /dev/null
+++ b/minepoch_py/momentum.py
@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+import sys
+import argparse
+import matplotlib.pyplot as plt
+import numpy as np
+
+
+def parse_arguments():
+    """Parse command line options.
+
+    """
+
+    parser = argparse.ArgumentParser(
+        description="""Momentum conservation analysis for minEPOCH
+        """,
+        formatter_class=argparse.ArgumentDefaultsHelpFormatter,
+    )
+
+    group = parser.add_argument_group("Tolerances")
+
+    group.add_argument(
+        "--momentum_conservation",
+        default=1e-4,
+        type=float,
+        help="Allowed fractional error in momentum conservation",
+        nargs="?",
+    )
+
+    parser.add_argument("--disable_plots", help="Disable plot generation",
+                        action="store_true")
+
+    return parser.parse_args()
+
+
+def get_momenta(fname='Data/momentum.dat'):
+    """Calculate time history of field and particle momentum for an output file.
+
+    Args:
+        fname: Input filename. Default: Data/momentum.dat
+
+    Returns:
+        times, particle_momentum, field_momentum
+    """
+
+    times = []
+    field_momenta = []
+    particle_momenta = []
+    with open(fname) as f:
+        # Skip header
+        _ = f.readline()
+        for line in f:
+            times.append(line.split()[1])
+            particle_momenta.append(line.split()[2:5])
+            field_momenta.append(line.split()[5:])
+
+    times = np.array(times, dtype=float)
+    particle_momenta = np.array(particle_momenta, dtype=float)
+    field_momenta = np.array(field_momenta, dtype=float)
+
+    return times, particle_momenta, field_momenta
+
+
+def momentum_check(fname='Data/momentum.dat', tolerance=None, label=None,
+                 plot=True, savefig=False, signedplot=True):
+    """Check quality of momentum conservation from minEPOCH simulation
+
+    Args:
+        fname: Input filename. Default: Data/momentum.dat
+        tolerance: Maximum acceptable fractional error. Default: None (no check)
+        label: Label for data set when plotting. Default: None
+        plot: Control optional plotting. Default: True
+        savefig: Control saving of figure. Default: False
+	signedplot: Plot +/- errors, or just absolute values. Default: True
+    """
+
+    # Calculate total energy as a function of time
+    times, pp, fp = get_momenta(fname)
+    total_p = np.sum((pp + fp)**2, axis=1) # Magnitude as a function of time
+    
+
+    # If plotting requested produce plot of energy conservation error as
+    # a function of time
+    if plot:
+        if signedplot:
+            data = total_p - total_p[0]
+        else:
+            data = np.abs(total_p - total_p[0])
+        plt.plot(times, data / total_p[0], label=label)
+        plt.xlabel(r'$\mathrm{t (s)}$', fontsize=16)
+        plt.ylabel(r'$\frac{\Delta |P|}{|P|(t=0)}$', fontsize=16)
+        plt.xlim(left=times[0])
+
+        # Update legend if necessary
+        if label is not None:
+            plt.legend()
+
+        plt.tight_layout()
+
+        if savefig:
+            plt.savefig('momentum_conservation.png')
+
+    # If tolerance provided, check final energy conservation error
+    if tolerance is not None:
+        delta_p = np.abs(total_p[-1] - total_p[0]) / total_p[0]
+        if delta_p > tolerance:
+            print('Momentum conservation (fractional) error = %.4E' % delta_p)
+            return 1
+        return 0
+
+    return None
+
+
+if __name__ == "__main__":
+    # Parse arguments
+    options = parse_arguments()
+    # Run error analysis
+    sys.exit(momentum_check(tolerance=options.momentum_conservation,
+                            plot=not options.disable_plots,
+                            savefig=True))
diff --git a/src/deck/deck.f90 b/src/deck/deck.f90
index 0de058a..9a58d4f 100644
--- a/src/deck/deck.f90
+++ b/src/deck/deck.f90
@@ -24,7 +24,8 @@ SUBROUTINE read_deck
          stdout_frequency, particle_push_start_time, n_species, &
          fixed_fields, global_substeps, use_esirkepov, n_field_probes, &
          explicit_pic, linear_tolerance, nonlinear_tolerance, &
-         verbose_solver, use_pseudo_current, pseudo_current_fac
+         verbose_solver, use_pseudo_current, pseudo_current_fac, &
+         write_momentum
     NAMELIST/field_probe_positions/ x_probes, y_probes, z_probes
 
     IF (first) THEN
diff --git a/src/io/calc_df.F90 b/src/io/calc_df.F90
index 477f363..53e5754 100644
--- a/src/io/calc_df.F90
+++ b/src/io/calc_df.F90
@@ -70,6 +70,93 @@ END SUBROUTINE calc_total_energy_sum
 
 
 
+  SUBROUTINE calc_total_momentum_sum
+
+    REAL(num) :: particle_px, particle_py, particle_pz
+    REAL(num) :: field_px, field_py, field_pz
+    REAL(num) :: part_w
+    REAL(num) :: ex_cc, ey_cc, ez_cc
+    REAL(num) :: bx_cc, by_cc, bz_cc
+    REAL(num) :: sum_out(6), sum_in(6)
+    REAL(num), PARAMETER :: c2 = c**2
+    INTEGER :: ispecies, i, j, k, im, jm, km
+    TYPE(particle), POINTER :: current
+    TYPE(particle_species), POINTER :: species, next_species
+
+    particle_px = 0.0_num
+    particle_py = 0.0_num
+    particle_pz = 0.0_num
+
+    ! Sum over all particles to calculate total momentum
+    next_species => species_list
+    DO ispecies = 1, n_species
+      species => next_species
+      next_species => species%next
+
+      current => species%attached_list%head
+      part_w = species%weight
+
+      DO WHILE (ASSOCIATED(current))
+        IF (particles_uniformly_distributed) THEN
+          part_w = current%weight
+        ENDIF
+        particle_px = particle_px + current%part_p(1) * part_w
+        particle_py = particle_py + current%part_p(2) * part_w
+        particle_pz = particle_pz + current%part_p(3) * part_w
+
+        current => current%next
+      ENDDO
+    ENDDO
+
+    ! Total EM field momentum
+    field_px = 0.0_num
+    field_py = 0.0_num
+    field_pz = 0.0_num
+
+    DO k = 1, nz
+      km  = k - 1
+      DO j = 1, ny
+        jm = j - 1
+        DO i = 1, nx
+          im = i - 1
+          ex_cc = 0.5_num  * (ex(im, j , k ) + ex(i , j , k ))
+          ey_cc = 0.5_num  * (ey(i , jm, k ) + ey(i , j , k ))
+          ez_cc = 0.5_num  * (ez(i , j , km) + ez(i , j , k ))
+
+          bx_cc = 0.25_num * (bx(i , jm, km) + bx(i , j , km) &
+                           +  bx(i , jm, k ) + bx(i , j , k ))
+          by_cc = 0.25_num * (by(im, j , km) + by(i , j , km) &
+                           +  by(im, j , k ) + by(i , j , k ))
+          bz_cc = 0.25_num * (bz(im, jm, k ) + bz(i , jm, k  ) &
+                           +  bz(im, j  ,k ) + bz(i , j , k  ))
+
+          field_px = field_px + (ey_cc * bz_cc - ez_cc * by_cc) / mu0
+          field_py = field_py + (ez_cc * bx_cc - ex_cc * bz_cc) / mu0
+          field_pz = field_pz + (ex_cc * by_cc - ey_cc * bx_cc) / mu0
+    ENDDO
+    ENDDO
+    ENDDO
+
+    sum_out(1) = particle_px
+    sum_out(2) = particle_py
+    sum_out(3) = particle_pz
+    sum_out(4) = field_px * dx * dy * dz / c2
+    sum_out(5) = field_py * dx * dy * dz / c2
+    sum_out(6) = field_pz * dx * dy * dz / c2
+
+    CALL MPI_REDUCE(sum_out, sum_in, 6, mpireal, MPI_SUM, 0, comm, errcode)
+
+    total_px_part = sum_in(1)
+    total_py_part = sum_in(2)
+    total_pz_part = sum_in(3)
+    total_px_field = sum_in(4)
+    total_py_field = sum_in(5)
+    total_pz_field = sum_in(6)
+
+  END SUBROUTINE calc_total_momentum_sum
+
+
+
   SUBROUTINE calc_charge_density(charge_density)
 
     REAL(num), INTENT(OUT), DIMENSION(1-ng:, 1-ng:, 1-ng:) :: charge_density
diff --git a/src/io/diagnostics.F90 b/src/io/diagnostics.F90
index e9ac86a..f6eefd9 100644
--- a/src/io/diagnostics.F90
+++ b/src/io/diagnostics.F90
@@ -49,6 +49,8 @@ SUBROUTINE output_routines(step, force_write)   ! step = step index
 
     IF (n_field_probes > 0) CALL write_field_probes(step)
 
+    IF (write_momentum) CALL momentum_history(step)
+
   END SUBROUTINE output_routines
 
 
@@ -298,4 +300,64 @@ SUBROUTINE time_history(step)   ! step = step index
 
   END SUBROUTINE time_history
 
+
+
+  SUBROUTINE momentum_history(step)   ! step = step index
+
+    INTEGER, INTENT(INOUT) :: step
+    CHARACTER(LEN=11+data_dir_max_length) :: full_filename
+    LOGICAL, SAVE :: first_call = .TRUE.
+    INTEGER :: errcode
+    INTEGER, PARAMETER :: fu = 67
+    LOGICAL, PARAMETER :: do_flush = .TRUE.
+    INTEGER, PARAMETER :: dump_frequency = 10
+
+    full_filename = TRIM(data_dir) // '/momentum.dat'
+
+    IF (first_call) THEN
+      ! open the file
+      IF (rank == 0) THEN
+        OPEN(unit=fu, status='REPLACE', file=TRIM(full_filename), &
+            iostat=errcode)
+        IF (errcode /= 0) THEN
+          PRINT*, 'Failed to open file: ', TRIM(full_filename)
+          CALL MPI_ABORT(MPI_COMM_WORLD, c_err_io, errcode)
+        END IF
+        WRITE(fu,'(''# '',a5,99a23)') 'step', &
+            'px_part', 'py_part', 'pz_part', &
+            'px_field', 'py_field', 'pz_field'
+        IF (do_flush) CLOSE(unit=fu)
+      ENDIF
+      first_call = .FALSE.
+    ENDIF
+
+    IF (MOD(step, dump_frequency) /= 0) RETURN
+
+    IF (timer_collect) THEN
+      IF (timer_walltime < 0.0_num) THEN
+        CALL timer_start(c_timer_io)
+      ELSE
+        CALL timer_start(c_timer_io, .TRUE.)
+      ENDIF
+    ENDIF
+
+    io_list => species_list
+
+    CALL calc_total_momentum_sum
+
+    IF (rank == 0) THEN
+      IF (do_flush) THEN
+        OPEN(unit=fu, status='OLD', position='APPEND', &
+            file=TRIM(full_filename), iostat=errcode)
+      ENDIF
+
+      WRITE(fu,'(i7,99e23.14)') step, time, &
+          total_px_part, total_py_part, total_pz_part, &
+          total_px_field, total_py_field, total_pz_field
+
+      IF (do_flush) CLOSE(unit=fu)
+    ENDIF
+
+  END SUBROUTINE momentum_history
+
 END MODULE diagnostics
diff --git a/src/shared_data.F90 b/src/shared_data.F90
index 4104ec4..1231633 100644
--- a/src/shared_data.F90
+++ b/src/shared_data.F90
@@ -422,6 +422,8 @@ MODULE shared_data
 
   INTEGER :: n_field_probes = 0
   INTEGER, DIMENSION(:,:), ALLOCATABLE :: field_probes
+  ! Output momentum time history
+  LOGICAL :: write_momentum = .TRUE.
 
   LOGICAL, DIMENSION(c_dir_x:c_dir_z,0:c_stagger_max) :: stagger
   INTEGER(i8) :: push_per_field = 5
@@ -433,8 +435,16 @@ MODULE shared_data
   REAL(num) :: laser_absorb_local = 0.0_num
   REAL(num) :: laser_injected = 0.0_num
   REAL(num) :: laser_absorbed = 0.0_num
-
+  ! Energy diagnostics
   REAL(num) :: total_particle_energy = 0.0_num
   REAL(num) :: total_field_energy = 0.0_num
+  ! Momentum diagnostics
+  REAL(num) :: total_px_part = 0.0_num
+  REAL(num) :: total_py_part = 0.0_num
+  REAL(num) :: total_pz_part = 0.0_num
+  REAL(num) :: total_px_field = 0.0_num
+  REAL(num) :: total_py_field = 0.0_num
+  REAL(num) :: total_pz_field = 0.0_num
+
 
 END MODULE shared_data
diff --git a/src/user_interaction/ic_module.f90 b/src/user_interaction/ic_module.f90
index b9d7f5d..9c6d259 100644
--- a/src/user_interaction/ic_module.f90
+++ b/src/user_interaction/ic_module.f90
@@ -27,6 +27,8 @@ SUBROUTINE custom_problem_setup(deck_state, problem)
     SELECT CASE (TRIM(problem))
     CASE('two_stream')
       CALL two_stream_setup(deck_state)
+    CASE('two_stream_neutral')
+      CALL two_stream_neutral_setup(deck_state)
     CASE('one_stream')
       CALL one_stream_setup(deck_state)
     CASE('drift_kin_default')
@@ -164,6 +166,166 @@ SUBROUTINE two_stream_setup(deck_state)
 
   END SUBROUTINE two_stream_setup
 
+  SUBROUTINE two_stream_neutral_setup(deck_state)
+
+    INTEGER, INTENT(IN) :: deck_state
+    REAL(num), PARAMETER :: v_drift = 0.2_num * c
+    REAL(num), PARAMETER :: v_therm = 0.01_num * c
+    REAL(num), PARAMETER :: v_pert = 0.1_num * v_therm
+    REAL(num), PARAMETER :: n0 = 8e11
+    INTEGER, PARAMETER :: ppc = 16
+    REAL(num) :: gamma_drift, temp_x, omega
+    INTEGER :: ix
+    TYPE(particle_species), POINTER :: current_species
+
+    IF (deck_state == c_ds_first) THEN
+      ! Set control variables here
+      nx_global = 64
+      ny_global = 4
+      nz_global = 4
+      x_min = 0.0_num
+      x_max = 2.0_num * pi
+      y_min = x_min
+      ! Could do (x_max * ny_global) / nx_global, but be wary of compilers
+      ! which don't obey precedence implied by parentheses by default
+      ! (e.g. Intel)
+      y_max = x_max * REAL(ny_global, num) / REAL(nx_global, num)
+      z_min = x_min
+      z_max = x_max * REAL(nz_global, num) / REAL(nx_global, num)
+
+      ! Plasma frequency
+      omega = SQRT(n0 * q0 * q0 / epsilon0 / m0)
+      t_end = 30.0_num / omega
+      stdout_frequency = 10
+       
+     ! dt_multiplier = 0.5
+
+
+      ! Need to set-up species here
+      NULLIFY(current_species)
+      CALL setup_species(current_species, 'Right')
+
+      ! mass -- MANDATORY
+      current_species%mass = 1.1_num * m0
+
+      ! charge -- MANDATORY
+      current_species%charge = -1.0_num * q0
+
+      ! npart_per_cell
+      current_species%npart_per_cell = ppc
+
+      ! MANDATORY
+      NULLIFY(current_species)
+      CALL setup_species(current_species, 'Left')
+
+      ! mass -- MANDATORY
+      current_species%mass = 1.0_num * m0
+
+      ! charge -- MANDATORY
+      current_species%charge = -1.0_num * q0
+
+      ! npart_per_cell
+      current_species%npart_per_cell = ppc
+
+     NULLIFY(current_species)
+      CALL setup_species(current_species, 'Balance')
+
+      ! mass -- MANDATORY
+      current_species%mass = 100 * m0
+
+      ! charge -- MANDATORY
+      current_species%charge = 1.0_num * q0
+
+      ! npart_per_cell
+      current_species%npart_per_cell = ppc
+
+      RETURN
+    END IF
+
+    ! Calculate gamma_drift
+    ! Strictly should be function of x, but vpert << vdrift
+    gamma_drift = 1.0_num / SQRT(1.0_num - (v_drift / c)**2)
+
+    ! Calculate (1 DoF) temperature
+    temp_x = v_therm**2 * m0 / kb
+
+    !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    ! Species
+
+    ! MANDATORY (Is the NULLIFY mandatory?)
+    NULLIFY(current_species)
+    CALL setup_species(current_species, 'Right')
+
+    ! density
+    current_species%density = n0
+
+    ! drift_x
+    ! Add on perturbation to seed instability
+    DO ix = 1-ng, nx+ng
+      current_species%drift(ix,:,:,1) = gamma_drift * current_species%mass &
+          * (v_drift + v_pert * SIN(3.0_num * x(ix)))
+    END DO
+
+    ! temp_x
+    current_species%temp(:,:,:,1) = temp_x
+
+    IF (explicit_pic) THEN
+      current_species%is_implicit = .FALSE.
+    ELSE
+      current_species%is_implicit = .TRUE.
+    END IF
+
+    !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    ! MANDATORY
+    NULLIFY(current_species)
+    CALL setup_species(current_species, 'Left')
+
+    ! density
+    current_species%density = n0
+
+    ! drift_x
+    ! Add on perturbation to seed instability
+    DO ix = 1-ng, nx+ng
+      current_species%drift(ix,:,:,1) = gamma_drift * current_species%mass &
+          * (-v_drift + v_pert * SIN(3.0_num * x(ix)))
+    END DO
+
+    ! temp_x
+    current_species%temp(:,:,:,1) = temp_x
+
+    IF (explicit_pic) THEN
+      current_species%is_implicit = .FALSE.
+    ELSE
+      current_species%is_implicit = .TRUE.
+    END IF
+
+    !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    
+       ! MANDATORY
+    NULLIFY(current_species)
+    CALL setup_species(current_species, 'Balance')
+
+    ! density
+    current_species%density = 2.0_num * n0
+
+    ! drift_x
+    DO ix = 1-ng, nx+ng
+      current_species%drift(ix,:,:,1) = 0.0_num
+    END DO
+
+    ! temp_x
+    current_species%temp(:,:,:,1) = temp_x
+
+    IF (explicit_pic) THEN
+      current_species%is_implicit = .FALSE.
+    ELSE
+      current_species%is_implicit = .TRUE.
+    END IF
+
+
+  END SUBROUTINE two_stream_neutral_setup
 
 
   SUBROUTINE em_wave_setup(deck_state)